[Arm, 1/3] Add -march=armv8.5-a and related internal feature macros to AArch32

[Arm, 1/3] Add -march=armv8.5-a and related internal feature macros to AArch32

This patch is part of the patch series to add support for ARMv8.5-A
extensions.

(https://developer.arm.com/products/architecture/cpu-architecture/a-profile/exploration-tools)

This is the first of the patch series and adds -march=armv8.5-a and
other internal feature marcos needed for it.

*** gas/ChangeLog ***

2018-10-05  Sudakshina Das  <sudi.das@arm.com>

	* config/tc-arm.c (arm_archs): New entry for armv8.5-a.
	(cpu_arch_ver): Likewise.
	* doc/c-arm.texi: Add documentation for the same.
	* testsuite/gas/arm/attr-march-armv8_5-a.d: New.

*** include/ChnageLog ***

2018-10-05  Sudakshina Das  <sudi.das@arm.com>

	* opcode/arm.h (ARM_EXT2_V8_5A): New.
	(ARM_AEXT2_V8_5A, ARM_ARCH_V8_5A): New.