[Aarch64] Add support for ARMv8.1 command line option

[Nicholas Clifton]

Hi Matthew,

> Ping.

oops - sorry,...

> include/opcode/
> 2015-06-03  Matthew Wahab  <matthew.wahab@arm.com>
>
>      * aarch64.h (AARCH64_V8_1): New.
>
> gas/
> 2015-06-03  Matthew Wahab  <matthew.wahab@arm.com>
>
>      * NEWS: Mention ARMv8.1 support in the Aarch64 port.
>      * config/tc-aarch64.c (aarch64_arch_option_table): Add
>      "armv8.1-a".
>      * doc/c-aarch64.texi (-march): Add "armv8.1-a".

Approved - please apply.

Cheers
   Nick