[AArch64] Add a "compnum" feature

[Nick Clifton]

Hi Richard,

> include/
> 	* opcode/aarch64.h (AARCH64_FEATURE_COMPNUM): New macro.
> 	(AARCH64_ARCH_V8_3): Include AARCH64_FEATURE_COMPNUM.
> 
> opcodes/
> 	* aarch64-tbl.h (aarch64_feature_simd_v8_3): Replace with...
> 	(aarch64_feature_compnum): ...this.
> 	(SIMD_V8_3): Replace with...
> 	(COMPNUM): ...this.
> 	(CNUM_INSN): New macro.
> 	(aarch64_opcode_table): Use it for the complex number instructions.
> 
> gas/
> 	* doc/c-aarch64.texi: Add a "compnum" entry.
> 	* config/tc-aarch64.c (aarch64_features): Likewise,
> 	* testsuite/gas/aarch64/advsimd-compnum.s: New test.
> 	* testsuite/gas/aarch64/advsimd-compnum.d: Likewise.

Approved for mainline.  Check with Tristan for the branch (but I think that it is getting very close to release time).

Cheers
  Nick