This prevents a compile error on Debian Jessie, when building from git.
This is fairly subtle, and Debian specific. It only happens when you use
autoreconf to generate a new libtool script. Debian patches that script
to require an explicit setting to link with all dependent libraries.
It should be harmless on other distros, and it does save us Debian guys some
hassle.
With this iteration, all the spice_codegen.py/proto/marshaller
generation has been moved to spice-common.
The spice-common directory will ship spice-protocol, since it's needed
there too to build libspice-common.
Again, make distcheck passes. Build with mingw & fedora linux.
The new configure flag '--with-gtk' can be used to choose
which GTK version to build against, defaulting to GTK2.
To enable GTK3 use
./configure --with-gtk=3.0
The libspice-client-glib-2.0.la library is unchanged, building
against glib-2.0 at all times.
The GTK3 build will produce a libspice-client-gtk-3.0.la
The include files will also live in $prefix/spice-client-gtk-3.0
and the pkgconfig is called spice-client-gtk-3.0 too.
This allows for full parallel install of GTK2 and GTK3 builds
