mep: Add C5 support

[Dave Brolley]

Frank Ch. Eigler wrote:
> Hi -
>
>   
>> This patch adds support for the MeP C5 core.  This adds a few new
>> opcodes, as well as extending (in a backward compatible way) some
>> existing opcodes.  Ok?
>>     
>
> I can't see anything grossly wrong.  If brolley doesn't have
> objections, you could consider yourself a maintainer of the port.
>
>   
I see no issues with the patch or with DJ being a maintainer of this port.

Dave