* spu-tdep.c: Include "observer.h".

	* spu-tdep.c: Include "observer.h".
	(spu_frame_unwind_cache): Unwind PC through overlay return stubs.
	(spu_overlay_data): New variable.
	(struct spu_overlay_table): New type.
	(spu_get_overlay_table, spu_overlay_update_osect, spu_overlay_update,
	spu_overlay_new_objfile): New functions.
	(spu_gdbarch_init): Install spu_overlay_update.
	(_initialize_spu_tdep): Register spu_overlay_new_objfile,
	allocate spu_overlay_data objfile data.