gcc.c: Document %{, in big comment at top.

gcc.c: Document %{, in big comment at top.

	* gcc.c: Document %{, in big comment at top.
	(input_suffix_matches): Remove special handling for .s and
	.S.
	(input_spec_matches): New.
	(handle_braces): Handle %{,.
	(validate_switches): ',' indicates a value which is not a switch.
	* config/alpha/osf.h (ASM_FINAL_SPEC): Use %{, rather than %{.
	to detect assembler input.
	* config/i386/sol2.h (CPP_SPEC): Likewise.
	* config/rs6000/sysv4.h (ASM_SPEC): Likewise.
	* config/rs6000/vxworks.h (ASM_SPEC): Likewise.
	* config/rs6000/lynx.h (ASM_SPEC): Likewise.
	* config/rs6000/linux64.h (ASM_SPEC_COMMON): Likewise.
	* config/i386/darwin.h (DARWIN_MINVERSION_SPEC): Objective-C plus
	-m64 causes deployment target to default to 10.5.
	* config/rs6000/darwin.h (DARWIN_MINVERSION_SPEC): Likewise.

From-SVN: r122783