[AArch64] Optimize .gnu.hash table size for executable

[Nick Clifton]

Hi Jiong,

>   OK for master?
> 
> 2017-01-17  Jiong Wang  <jiong.wang@arm.com>
> bfd/
>         * elfnn-aarch64.c (elf_aarch64_hash_symbol): New function.
>         (elf_backend_hash_symbol): Define.
> 
> ld/
>         * testsuite/ld-aarch64/aarch64-elf.exp (aarch64elflinktests): New tests.
>         * testsuite/ld-aarch64/func-in-so.s: New test source file.
>         * testsuite/ld-aarch64/func-sym-hash-opt.s: Likewise.
>         * testsuite/ld-aarch64/func-sym-hash-opt.d: New expected test result.

Approved - please apply.

Cheers
  Nick