Reviewed the use of MAEMO_GTK define, now we add the define in the compilation line...

Reviewed the use of MAEMO_GTK define, now we add the define in the compilation line, and we also add it to the pc file.

* configure.ac: Added MAEMO_GTK define to the compilation command
	and removed it from the config.h.

	* pkgconfig/hildon.pc.in: Added MAEMO_GTK, that way applications
	do not have to take care about this define if the library was
	compiled with it.

	* src/hildon-gtk.c:
	* src/hildon-gtk.h: Replaced MAEMO_CHANGES with MAEMO_GTK.