Build libgirepository as a GLib sub-library

The introspection API has lived out of tree far too long. It has the
same ABI guarantees as the rest of GLib, so it has no reason to be split
from the main library.

The gobject-introspection project can depend on libgirepository, and the
language bindings can drop the gobject-introspection-1.0 dependency.

girepository/gitypes.h

@@ -27,8 +27,6 @@
 #error "Only <girepository.h> can be included directly."
 #endif
 
-#include <giversionmacros.h>
-
 G_BEGIN_DECLS
 
 typedef struct _GIBaseInfoStub {
@@ -513,4 +511,3 @@ typedef struct _GITypelib GTypelib;
 G_END_DECLS
 
 #endif  /* __GITYPES_H__ */
-