m4: Update manywarnings from gnulib

Fixes these noisy errors on Fedora 21:

gcc: warning: switch '-Wmudflap' is no longer supported

m4/manywarnings.m4

@@ -1,5 +1,5 @@
-# manywarnings.m4 serial 3
-dnl Copyright (C) 2008-2012 Free Software Foundation, Inc.
+# manywarnings.m4 serial 7
+dnl Copyright (C) 2008-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -35,14 +35,12 @@ AC_DEFUN([gl_MANYWARN_COMPLEMENT],
 # make sure your gcc understands it.
 AC_DEFUN([gl_MANYWARN_ALL_GCC],
 [
-  dnl First, check if -Wno-missing-field-initializers is needed.
-  dnl -Wmissing-field-initializers is implied by -W, but that issues
-  dnl warnings with GCC version before 4.7, for the common idiom
-  dnl of initializing types on the stack to zero, using { 0, }
+  dnl First, check for some issues that only occur when combining multiple
+  dnl gcc warning categories.
   AC_REQUIRE([AC_PROG_CC])
   if test -n "$GCC"; then
 
-    dnl First, check -W -Werror -Wno-missing-field-initializers is supported
+    dnl Check if -W -Werror -Wno-missing-field-initializers is supported
     dnl with the current $CC $CFLAGS $CPPFLAGS.
     AC_MSG_CHECKING([whether -Wno-missing-field-initializers is supported])
     AC_CACHE_VAL([gl_cv_cc_nomfi_supported], [
@@ -77,108 +75,171 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
       ])
       AC_MSG_RESULT([$gl_cv_cc_nomfi_needed])
     fi
+
+    dnl Next, check if -Werror -Wuninitialized is useful with the
+    dnl user's choice of $CFLAGS; some versions of gcc warn that it
+    dnl has no effect if -O is not also used
+    AC_MSG_CHECKING([whether -Wuninitialized is supported])
+    AC_CACHE_VAL([gl_cv_cc_uninitialized_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -Werror -Wuninitialized"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_uninitialized_supported=yes],
+        [gl_cv_cc_uninitialized_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_uninitialized_supported])
+
   fi
 
+  # List all gcc warning categories.
+  # To compare this list to your installed GCC's, run this Bash command:
+  #
+  # comm -3 \
+  #  <(sed -n 's/^  *\(-[^ ]*\) .*/\1/p' manywarnings.m4 | sort) \
+  #  <(gcc --help=warnings | sed -n 's/^  \(-[^ ]*\) .*/\1/p' | sort |
+  #      grep -v -x -f <(
+  #         awk '/^[^#]/ {print $1}' ../build-aux/gcc-warning.spec))
+
   gl_manywarn_set=
   for gl_manywarn_item in \
-    -Wall \
     -W \
-    -Wformat-y2k \
-    -Wformat-nonliteral \
-    -Wformat-security \
-    -Winit-self \
-    -Wmissing-include-dirs \
-    -Wswitch-default \
-    -Wswitch-enum \
-    -Wunused \
-    -Wunknown-pragmas \
-    -Wstrict-aliasing \
-    -Wstrict-overflow \
-    -Wsystem-headers \
-    -Wfloat-equal \
-    -Wtraditional \
-    -Wtraditional-conversion \
-    -Wdeclaration-after-statement \
-    -Wundef \
-    -Wshadow \
-    -Wunsafe-loop-optimizations \
-    -Wpointer-arith \
-    -Wbad-function-cast \
-    -Wc++-compat \
-    -Wcast-qual \
-    -Wcast-align \
-    -Wwrite-strings \
-    -Wconversion \
-    -Wsign-conversion \
-    -Wlogical-op \
-    -Waggregate-return \
-    -Wstrict-prototypes \
-    -Wold-style-definition \
-    -Wmissing-prototypes \
-    -Wmissing-declarations \
-    -Wmissing-noreturn \
-    -Wmissing-format-attribute \
-    -Wpacked \
-    -Wpadded \
-    -Wredundant-decls \
-    -Wnested-externs \
-    -Wunreachable-code \
-    -Winline \
-    -Winvalid-pch \
-    -Wlong-long \
-    -Wvla \
-    -Wvolatile-register-var \
-    -Wdisabled-optimization \
-    -Wstack-protector \
-    -Woverlength-strings \
-    -Wbuiltin-macro-redefined \
-    -Wmudflap \
-    -Wpacked-bitfield-compat \
-    -Wsync-nand \
-    ; do
-    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
-  done
-  # The following are not documented in the manual but are included in
-  # output from gcc --help=warnings.
-  for gl_manywarn_item in \
-    -Wattributes \
-    -Wcoverage-mismatch \
-    -Wmultichar \
-    -Wunused-macros \
-    ; do
-    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
-  done
-  # More warnings from gcc 4.6.2 --help=warnings.
-  for gl_manywarn_item in \
     -Wabi \
+    -Waddress \
+    -Waggressive-loop-optimizations \
+    -Wall \
+    -Warray-bounds \
+    -Wattributes \
+    -Wbad-function-cast \
+    -Wbuiltin-macro-redefined \
+    -Wcast-align \
+    -Wchar-subscripts \
+    -Wclobbered \
+    -Wcomment \
+    -Wcomments \
+    -Wcoverage-mismatch \
     -Wcpp \
+    -Wdate-time \
     -Wdeprecated \
     -Wdeprecated-declarations \
+    -Wdisabled-optimization \
     -Wdiv-by-zero \
     -Wdouble-promotion \
+    -Wempty-body \
     -Wendif-labels \
+    -Wenum-compare \
     -Wextra \
     -Wformat-contains-nul \
     -Wformat-extra-args \
+    -Wformat-nonliteral \
+    -Wformat-security \
+    -Wformat-y2k \
     -Wformat-zero-length \
-    -Wformat=2 \
+    -Wfree-nonheap-object \
+    -Wignored-qualifiers \
+    -Wimplicit \
+    -Wimplicit-function-declaration \
+    -Wimplicit-int \
+    -Winit-self \
+    -Winline \
+    -Wint-to-pointer-cast \
+    -Winvalid-memory-model \
+    -Winvalid-pch \
+    -Wjump-misses-init \
+    -Wlogical-op \
+    -Wmain \
+    -Wmaybe-uninitialized \
+    -Wmissing-braces \
+    -Wmissing-declarations \
+    -Wmissing-field-initializers \
+    -Wmissing-include-dirs \
+    -Wmissing-parameter-type \
+    -Wmissing-prototypes \
     -Wmultichar \
-    -Wnormalized=nfc \
+    -Wnarrowing \
+    -Wnested-externs \
+    -Wnonnull \
+    -Wold-style-declaration \
+    -Wold-style-definition \
+    -Wopenmp-simd \
     -Woverflow \
+    -Woverlength-strings \
+    -Woverride-init \
+    -Wpacked \
+    -Wpacked-bitfield-compat \
+    -Wparentheses \
+    -Wpointer-arith \
+    -Wpointer-sign \
     -Wpointer-to-int-cast \
     -Wpragmas \
+    -Wreturn-local-addr \
+    -Wreturn-type \
+    -Wsequence-point \
+    -Wshadow \
+    -Wsizeof-pointer-memaccess \
+    -Wstack-protector \
+    -Wstrict-aliasing \
+    -Wstrict-overflow \
+    -Wstrict-prototypes \
     -Wsuggest-attribute=const \
+    -Wsuggest-attribute=format \
     -Wsuggest-attribute=noreturn \
     -Wsuggest-attribute=pure \
+    -Wswitch \
+    -Wswitch-default \
+    -Wsync-nand \
+    -Wsystem-headers \
     -Wtrampolines \
+    -Wtrigraphs \
+    -Wtype-limits \
+    -Wuninitialized \
+    -Wunknown-pragmas \
+    -Wunsafe-loop-optimizations \
+    -Wunused \
+    -Wunused-but-set-parameter \
+    -Wunused-but-set-variable \
+    -Wunused-function \
+    -Wunused-label \
+    -Wunused-local-typedefs \
+    -Wunused-macros \
+    -Wunused-parameter \
+    -Wunused-result \
+    -Wunused-value \
+    -Wunused-variable \
+    -Wvarargs \
+    -Wvariadic-macros \
+    -Wvector-operation-performance \
+    -Wvla \
+    -Wvolatile-register-var \
+    -Wwrite-strings \
+    \
     ; do
     gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
   done
 
-  # Disable the missing-field-initializers warning if needed
+  # gcc --help=warnings outputs an unusual form for this option; list
+  # it here so that the above 'comm' command doesn't report a false match.
+  gl_manywarn_set="$gl_manywarn_set -Wnormalized=nfc"
+
+  # These are needed for older GCC versions.
+  if test -n "$GCC"; then
+    case `($CC --version) 2>/dev/null` in
+      'gcc (GCC) '[[0-3]].* | \
+      'gcc (GCC) '4.[[0-7]].*)
+        gl_manywarn_set="$gl_manywarn_set -fdiagnostics-show-option"
+        gl_manywarn_set="$gl_manywarn_set -funit-at-a-time"
+          ;;
+    esac
+  fi
+
+  # Disable specific options as needed.
   if test "$gl_cv_cc_nomfi_needed" = yes; then
     gl_manywarn_set="$gl_manywarn_set -Wno-missing-field-initializers"
   fi
 
+  if test "$gl_cv_cc_uninitialized_supported" = no; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-uninitialized"
+  fi
+
   $1=$gl_manywarn_set
 ])