* target.def (legitimate_combined_insn): New target hook.
	* doc/tm.texi.in (TARGET_LEGITIMATE_COMBINED_INSN): New hook.
	* doc/tm.texi: Regenerated.
	* combine.c (recog_for_combine): Call targetm.legitimate_combined_insn
	to allow targets to reject combined insn.
	* hooks.h (hook_bool_rtx_true): New.
	* hooks.c (hook_bool_rtx_true): Ditto.

From-SVN: r190846