Previously we would require applications that shipped with private
typelibs to add the private path to LD_LIBRARY_PATH, or to have a
launcher binary with the right RPATH.
Now they can just call GIRepository.prepend_library_path() before
they access the module.
https://bugzilla.gnome.org/show_bug.cgi?id=694485
Rather than having a regex for both builds, but *also* use a symbol
file for the MSVC build which would bitrot quickly, force us to update
the .symbols file by using it for Unix too.
Add some missing symbols.
This is the listing of symbols to export from the main libgirepository
.dll/.so. This is used for example to generate the .lib file from the
Windows DLL.
https://bugzilla.gnome.org/show_bug.cgi?id=681820
