* rsvg.h:
	* rsvg.c: (rsvg_pixbuf_from_file), (rsvg_pixbuf_from_file_at_zoom),
	(rsvg_pixbuf_from_file_at_size): Take const char *, not char *.

	* test-rsvg.c: (main): Remove unneeded casts. Restore the error
	message for the case when the parser doesn't parse anything.