MIR Serialization: Serialize the sub register indices.

[Duncan P. N. Exon Smith]

> On 2015-Jul-13, at 09:56, Alex L <arphaman at gmail.com> wrote:
> 
> Hello,
> 
> This patch serializes the sub register indices from the register machine operands.
> A subregister index can be specified after the register in the operand using the following
> syntax:
> 
>   <register> [ : <subregister> ]
> 
> Cheers,
> Alex
> <0001-MIR-Serialization-serialize-the-subregister-indices.patch>

LGTM.