[PATCH, MIPS, Ping] Inline memcpy for MipsR6

[Simon Dardis]

Hello,

> This patch enables inline memcpy for R6 which was previously disabled and 
> adds support for expansion when source and destination are at least half-word 
> aligned.

https://gcc.gnu.org/ml/gcc-patches/2015-07/msg00749.html

Thanks,
Simon