[Arm, 2/3] Add instruction SB for AArch32

[Arm, 2/3] Add instruction SB for 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 patch adds the instruction SB. 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 adding a
new "+sb" for older archtectures.

*** include/ChangeLog ***

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

	* opcode/arm.h (ARM_EXT2_SB): New.
	(ARM_ARCH_V8_5A): Add ARM_EXT2_SB by default.

*** opcodes/ChangeLog ***

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

	* arm-dis.c (arm_opcodes): Add sb.
	(thumb32_opcodes): Likewise.

*** gas/ChangeLog ***

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

	* config/tc-arm.c (arm_ext_sb): New.
	(insns): Add new sb instruction.
	(arm_extensions): Add "sb".
	* doc/c-arm.texi: Document the above.
	* testsuite/gas/arm/sb-bad.d: New test.
	* testsuite/gas/arm/sb-bad.l: New test.
	* testsuite/gas/arm/sb-thumb1.d: New test.
	* testsuite/gas/arm/sb-thumb2.d: New test.
	* testsuite/gas/arm/sb.s: New test.
	* testsuite/gas/arm/sb1.d: New test.
	* testsuite/gas/arm/sb2.d: New test.