This is the next part of breaking up #518 into smaller PRs.
This is the rest of the commits which change the existing
`THREAD_MODEL=posix` functionality. It:
* _removes_ some functions which are optional and which were already
nonfunctional.
* (Continues to) establish a precedent of trying to remain as compatible
with Open Group specifications as possible, even when there are major
differences in WASI capabilities (i.e. thread cancellation)
Compared to the RFC PR, the `pthread_atfork` stub has been dropped as it
is now officially obsolete as of the very recent Issue 8 of the
specifications.
See the WHATSNEW file for details. The biggest change in musl is the
switch to 64-bit time_t for 32-bit targets, however WASI libc was already
using 64-bit time_t. The main change affecting WASI is an update to
Unicode 12.1.0.
See the WHATSNEW file for details; this doesn't have any major changes
for wasi-libc; in particular, the new catgets and GLOB_TILDE features
are disabled.
And clean up various stale declarations and macros that this turned up.
In particular:
- Don't install pthread.h or aio.h in THREAD_MODEL=single mode.
- Don't define mkstemp and friends, since WASI currently has no support for
temporary directories.
