New target macros for getting at the pc, sp and fp.

	New target macros for getting at the pc, sp and fp.
	* infcmd.c (read_pc, write_pc):  Modify to use new macros.
	(read_sp, write_sp, read_fp, write_fp): New functions.
	* blockframe.c (reinit_frame_cache, get_prev_frame_info):  Use new functions.
	* breakpoint.c (bpstat_alloc): ditto.
	* infrun.c (wait_for_inferior): ditto.
	* stack.c (print_frame_info): ditto.
	* valops (call_function_by_hand): ditto.
	* corelow.c (core_open): ditto.
	* h8500-tdep.c: (target_read_sp, target_write_sp, target_read_pc,
	target_write_pc, target_read_fp, target_write_fp): New functions.
	* inferior.h (read_sp, write_sp, read_fp, write_fp): Prototypes.