Generate GdkPixdata introspection
The GdkPixdata API is built as part of the GdkPixbuf shared library, but:
- it has its own namespace
- it has its own header file
- it's mostly meant for C applications
- it is deprecated
Consumers of the introspection data cannot access this API by using the GdkPixbuf-2.0 GIR, as the namespace and included headers are different.
Instead of kludging the API, let's move the GdkPixdata introspection out of the GdkPixbuf-2.0 GIR and into its own module.
This is an introspection ABI break, but there aren't many consumers of GdkPixdata out there, and it's preferable to straight including the gdk-pixdata.h header into gdk-pixbuf.h.
Fixes #72 (closed)