Add support for the MIPS eXtended Physical Address (XPA) ASE.

Add support for the MIPS eXtended Physical Address (XPA) ASE.

ChangeLog:

binutils/
	* doc/binutils.texi: Document the disassemble MIPS XPA instructions
	command line option.

gas/
	* config/tc-mips.c (options): Add OPTION_XPA and OPTION_NO_XPA.
 	(md_longopts): Add xpa and no-xpa command line options.
 	(mips_ases): Add MIPS XPA ASE.
 	(mips_cpu_info_table): Update p5600 entry to allow the XPA ASE.
 	* doc/as.texinfo: Document the MIPS XPA command line options.
 	* doc/c-mips.texi: Document the MIPS XPA command line options,
 	and assembler directives.

gas/testsuite/
 	* gas/mips/mips.exp: Add xpa tests.
 	* gas/mips/xpa.s: New test.
 	* gas/mips/xpa.d: Likewise.

include/
 	* opcode/mips.h (ASE_XPA): New define.

opcodes/
 	* mips-dis.c (mips_arch_choices): Update mips32r2 and mips64r2
 	to allow the MIPS XPA ASE.
 	(parse_mips_dis_option): Process the -Mxpa option.
 	* mips-opc.c (XPA): New define.
 	(mips_builtin_opcodes): Add MIPS XPA instructions and move the
 	locations of the ctc0 and cfc0 instructions.