sibcall.c (skip_copy_to_return_value): Call identify_call_return_value here,...

sibcall.c (skip_copy_to_return_value): Call identify_call_return_value here, and return orig_insn if it returns zero.

	* sibcall.c (skip_copy_to_return_value): Call
	identify_call_return_value here, and return orig_insn if it
	returns zero.  Hardret and softret arguments now unnecessary.
	(call_ends_block_p): Don't call identify_call_return_value here.

	* ggc-common.c (ggc_mark_rtx_children): No need to mark 'S' or
	's' slots in RTXen.
	* ggc-page.c, ggc-simple.c (ggc_mark_if_gcable): Delete	function.
	* ggc.h (ggc_mark_if_gcable): Delete prototype.

testsuite:
	* g77.dg: New directory.
	* g77.dg/20010216-1.f: New test case.
	* g77.dg/dg.exp: New driver.
	* lib/g77-dg.exp: New driver library.

From-SVN: r39916