[PATCH, BINUTILS, AARCH64, 3/9] Add instruction SB for ARMv8.5-A

[PATCH, BINUTILS, AARCH64, 3/9] Add instruction SB for ARMv8.5-A

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/docs/ddi0596/a/a64-base-instructions-alphabetic-order)

This instruction is retrospectively made optional for all versions of
the architecture from ARMv8.0 to ARMv8.4 and is mandatory from
ARMv8.5.  Hence a new command line option of "+sb" is added for older
architectures.

*** include/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* opcode/aarch64.h (AARCH64_FEATURE_SB): New.
	(AARCH64_ARCH_V8_5): Add AARCH64_FEATURE_SB by default.

*** opcodes/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* aarch64-tbl.h (aarch64_feature_sb): New.
	(SB, SB_INSN): New.
	(aarch64_opcode_table): Add entry for sb.
	* aarch64-asm-2.c: Regenerate.
	* aarch64-dis-2.c: Regenerate.
	* aarch64-opc-2.c: Regenerate.

*** gas/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* config/tc-aarch64.c (aarch64_features): Add new "sb" option
	for older architectures.
	* doc/c-aarch64.texi: Document the same.
	* testsuite/gas/aarch64/sb.s: New.
	* testsuite/gas/aarch64/sb.d: New.