x86: Replace IgnoreSize/DefaultSize with MnemonicSize

Since an instruction template can't have both IgnoreSize and DefaultSize,
this patch replaces IgnoreSize and DefaultSize with MnemonicSize.

gas/

	* config/tc-i386.c (match_template): Replace ignoresize and
	defaultsize with mnemonicsize.
	(process_suffix): Likewise.

opcodes/

	* i386-gen.c (opcode_modifiers): Replace IgnoreSize/DefaultSize
	with MnemonicSize.
	* i386-opc.h (IGNORESIZE): New.
	(DEFAULTSIZE): Likewise.
	(IgnoreSize): Removed.
	(DefaultSize): Likewise.
	(MnemonicSize): New.
	(i386_opcode_modifier): Replace ignoresize/defaultsize with
	mnemonicsize.
	* i386-opc.tbl (IgnoreSize): New.
	(DefaultSize): Likewise.
	* i386-tbl.h: Regenerated.