[BINUTILS, AARCH64, 1/8] Add support for Memory Tagging Extension for ARMv8.5-A

[BINUTILS, AARCH64, 1/8] Add support for Memory Tagging Extension for ARMv8.5-A

This patch is part of the patch series to add support for ARMv8.5-A
Memory Tagging Extensions. Memory Tagging Extension is an optional extension to
ARMv8.5-A and is enabled using the +memtag command line option.
This patch adds the new command line option and the new feature macros.

*** include/ChangeLog ***

2018-11-12  Sudakshina Das  <sudi.das@arm.com>

	* opcode/aarch64.h (AARCH64_FEATURE_MEMTAG): New.

*** opcodes/ChangeLog ***

2018-11-12  Sudakshina Das  <sudi.das@arm.com>

	* aarch64-tbl.h (aarch64_feature_memtag): New.
	(MEMTAG, MEMTAG_INSN): New.

*** gas/ChangeLog ***

2018-11-12  Sudakshina Das  <sudi.das@arm.com>

	* config/tc-aarch64.c (aarch64_features): Add "memtag"
	as a new option.
	* doc/c-aarch64.texi: Document the same.