[AArch64] Add ARMv8.3 combined pointer authentication branch instructions

[AArch64] Add ARMv8.3 combined pointer authentication branch instructions

Add support for ARMv8.3 pointer authentication instructions
that are encoded as unconditional branch instructions.

opcodes/
2016-11-11  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* aarch64-tbl.h (arch64_opcode_table): Add braa, brab, blraa, blrab, braaz,
	brabz, blraaz, blrabz, retaa, retab, eretaa, eretab.
	* aarch64-asm-2.c: Regenerate.
	* aarch64-dis-2.c: Regenerate.
	* aarch64-opc-2.c: Regenerate.

gas/
2016-11-08  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* testsuite/gas/aarch64/pac.s: Add ARMv8.3 branch instruction tests.
	* testsuite/gas/aarch64/pac.d: Likewise.