Sparc flat register window support.

	Sparc flat register window support.
	* sparc-tdep.c (sparc_insn_layout): New union, defines layout of
        instructions symbolically (used to be local to skip_prologue).
	(sparc_init_extra_frame_info): New function.
	(sparc_frame_chain): Add flat cases throughout.
	(skip_prologue): Add recognition of flat prologues.
	(sparc_frame_find_saved_regs): Add flat cases.
	(sparc_pop_frame): Ditto.
	* config/sparc/tm-sparc.h (EXTRA_FRAME_INFO): New slots.
	(INIT_EXTRA_FRAME_INFO): Call sparc_init_extra_frame_info.
	(PRINT_EXTRA_FRAME_INFO): Define.