* gdk/gdkdisplay.h
* gdk/gdkdrawable.h
* gdk/gdkevents.h
* gdk/gdkpango.h
* gdk/gdkregion.h
* gdk/gdkrgb.h
* gdk/gdkwindow.h: made more struct pointer and array parameters
const. GDK should now be constified as far as possible without
breaking source compatibility. Includes some minor cleanup like
indentation and s/nfoo/n_foo/ (bug #508544).