GCC complains about non-static functions being defined without a
previous prototype, even if they themselves provide one.

https://bugzilla.gnome.org/show_bug.cgi?id=793399

Properly define GLIB/GOBJECT_STATIC_COMPILATION when static build is enabled.
Use library() instead of shared_library() to allow selecting static builds.

https://bugzilla.gnome.org/show_bug.cgi?id=784995

Some platforms use different extensions for compile-time linkable
libraries vs runtime-loadable modules. Need to use special libtool
flag in the latter case for consistency with what gmodule expects.

https://bugzilla.gnome.org/show_bug.cgi?id=731703

giomodule test needed symbol visibility pragmas added. This is needed on
Windows anyway, so it's better to do it this way rather than disabling
-fvisibility=hidden for the test modules.

Disable gio tests on Windows, fix .gitignore to not ignore
config.h.meson, and add more things to it.

Rename the library file naming and versioning to match what Autotools
outputs, e.g., libglib-2.0.so.0.5000.2 on Linux, libglib-2.0-0.dll  and
glib-2.0-0.dll on Windows with MSVC.

Several more tiny fixes, more executables built and installed, install
pkg-config and m4 files, fix building of gobject tests.

Changes to gdbus-codegen to support out-of-tree builds without
environment variables set (which you can't in Meson). We now add the
build directory to the Python module search path.

Several small fixes to the build files.

Lots of tests have also been added, and glib tests pass now.

http://lists.gnu.org/archive/html/bug-libtool/2013-05/msg00009.html hit
us again.  libtool only builds .so files if we install the library, so
force it to build for our testcase, even if we don't install it.

If installed tests are not enabled, installed_testdir is not
defined, so we end up trying to create /modules and to chmod
things in /x-content/, which is not right.

Add a dedicated test for GIOModule.