Add support for monitorx/mwaitx instructions

Add support for monitorx/mwaitx instructions

gas/

	* config/tc-i386.c (cpu_arch): Add .mwaitx.
	(process_immext): Check operands for monitorx/mwaitx instructions.
	* doc/c-i386.texi: Document mwaitx.

gas/testsuite/

	* gas/i386/i386.exp: Add new mwaitx test cases.
	* gas/i386/mwaitx.s: New.
	* gas/i386/mwaitx-bdver4.d: New.
	* gas/i386/x86-64-mwaitx.s: New.
	* gas/i386/x86-64-mwaitx-bdver4.d: New.
	* gas/i386/mwaitx-reg.s: New.
	* gas/i386/mwaitx-reg.l: New.
	* gas/i386/x86-64-mwaitx-reg.l: New.
	* gas/i386/x86-64-mwaitx-reg.s: New.
	* gas/i386/arch-13.s: Updated.
	* gas/i386/arch-13.d: Updated.
	* gas/i386/arch-13-znver1.d: Updated.
	* gas/i386/x86-64-arch-3.s: Updated.
	* gas/i386/x86-64-arch-3.d: Updated.
	* gas/i386/x86-64-arch-3-znver1.d: Updated.

opcodes/

	* i386-dis.c (OP_Mwaitx): New.
	(rm_table): Add monitorx/mwaitx.
	* i386-gen.c (cpu_flag_init): Add CpuMWAITX to CPU_BDVER4_FLAGS
	and CPU_ZNVER1_FLAGS.  Add CPU_MWAITX_FLAGS.
	(operand_type_init): Add CpuMWAITX.
	* i386-opc.h (CpuMWAITX): New.
	(i386_cpu_flags): Add cpumwaitx.
	* i386-opc.tbl: Add monitorx and mwaitx.
	* i386-init.h: Regenerated.
	* i386-tbl.h: Likewise.