[AArch64] Add ARMv8.3 pointer authentication key registers

[AArch64] Add ARMv8.3 pointer authentication key registers

Add support for system registers introduced in ARMv8.3
for pointer authentication.

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

	* aarch64-opc.c (aarch64_sys_regs): Add apiakeylo_el1, apiakeyhi_el1,
	apibkeylo_el1, apibkeyhi_el1, apdakeylo_el1, apdakeyhi_el1,
	apdbkeylo_el1, apdbkeyhi_el1, apgakeylo_el1 and apgakeyhi_el1.
	(aarch64_sys_reg_supported_p): Add feature test for new registers.

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

	* testsuite/gas/aarch64/sysreg-3.s: New.
	* testsuite/gas/aarch64/sysreg-3.d: New.
	* testsuite/gas/aarch64/illegal-sysreg-3.l: New.
	* testsuite/gas/aarch64/illegal-sysreg-3.d: New.