Add tailcall/sibcall support to the H8

Add tailcall/sibcall support to the H8

gcc/

	* config/h8300/h8300-protos.h (h8300_expand_epilogue): Add new
	argument.
	* config/h8300/jumpcall.md (call, call_value): Restrict to
	!SIBLING_CALL_P cases.
	(subcall, sibcall_value): New patterns & expanders.
	* config/h8300/proepi.md (epilogue): Pass new argument to
	h8300_expand_epilogue.
	(sibcall_epilogue): New expander.
	* config/h8300/h8300.c (h8300_expand_epilogue): Handle sibcall
	epilogues too.
	(h8300_ok_for_sibcall_p): New function.
	(TARGET_FUNCTION_OK_FOR_SIBCALL): define.