Explicitely add needed include arguments as well as linker arguments
for gmodule. Before this change we relied on gmodule being an implicit
dependency pulled in via the gtk+-2.0 module, this does not seem to be
the case anymore with >=gdk-pixbuf-2.24 and >=pango-1.30.
Thanks for Alexandre Rostovtsev for bringing this up on the mailinglist
and for providing a first patch.
See also https://bugs.gentoo.org/show_bug.cgi?id=428532
8abd662cd6