[PATCH] metag: add extern C to header

[Nick Clifton]

Hi Trev,

> include/ChangeLog:
> 2016-05-25  Trevor Saunders  <tbsaunde+binutils@tbsaunde.org>
> 
> 	* opcode/metag.h: wrap declarations in extern "C".
 
Approved - please apply.

Cheers
  Nick