x86: Add -mmwait for -mgeneral-regs-only

x86: Add -mmwait for -mgeneral-regs-only

Add -mmwait so that the MWAIT and MONITOR intrinsics can be used with
-mgeneral-regs-only and make -msse3 to imply -mmwait.

gcc/

	* config.gcc: Install mwaitintrin.h for i[34567]86-*-* and
	x86_64-*-* targets.
	* common/config/i386/i386-common.c (OPTION_MASK_ISA2_MWAIT_SET):
	New.
	(OPTION_MASK_ISA2_MWAIT_UNSET): Likewise.
	(ix86_handle_option): Handle -mmwait.
	* config/i386/i386-builtins.c (ix86_init_mmx_sse_builtins):
	Replace OPTION_MASK_ISA_SSE3 with OPTION_MASK_ISA2_MWAIT on
	__builtin_ia32_monitor and __builtin_ia32_mwait.
	* config/i386/i386-options.c (isa2_opts): Add -mmwait.
	(ix86_valid_target_attribute_inner_p): Likewise.
	(ix86_option_override_internal): Enable mwait/monitor
	instructions for -msse3.
	* config/i386/i386.h (TARGET_MWAIT): New.
	(TARGET_MWAIT_P): Likewise.
	* config/i386/i386.opt: Add -mmwait.
	* config/i386/mwaitintrin.h: New file.
	* config/i386/pmmintrin.h: Include <mwaitintrin.h>.
	* config/i386/sse.md (sse3_mwait): Replace TARGET_SSE3 with
	TARGET_MWAIT.
	(@sse3_monitor_<mode>): Likewise.
	* config/i386/x86gprintrin.h: Include <mwaitintrin.h>.
	* doc/extend.texi: Document mwait target attribute.
	* doc/invoke.texi: Document -mmwait.

gcc/testsuite/

	* gcc.target/i386/monitor-2.c: New test.