darwin.h (LINK_SPEC): Always pass -macosx_version_min to linker.

darwin.h (LINK_SPEC): Always pass -macosx_version_min to linker.

	* config/darwin.h (LINK_SPEC): Always pass -macosx_version_min
	to linker.
	(DARWIN_EXTRA_SPECS): Add %(darwin_minversion).
	* config/rs6000/darwin.h (SUBTARGET_OVERRIDE_OPTIONS): Just call
	darwin_rs6000_override_options.
	(C_COMMON_OVERRIDE_OPTIONS): Expect
	darwin_macosx_version_min to be non-NULL always.
	(TARGET_C99_FUNCTIONS): Likewise.
	(CC1_SPEC): Always pass -mmacosx-version-min to cc1*.
	(DARWIN_MINVERSION_SPEC): New.
	* config/rs6000/rs6000.c (darwin_rs6000_override_options): New.
	* config/i386/darwin.h (CC1_SPEC): Always pass -mmacosx-version-min
	to cc1*.
	(DARWIN_MINVERSION_SPEC): New.
	* config/darwin.opt (mmacosx-version-min): Initialize to non-NULL
	value.
	* config/darwin-c.c (darwin_cpp_builtins): Expect
	darwin_macosx_version_min to be non-NULL always.

From-SVN: r122067