Patch for faster memcpy on MIPS

[Ellcey, Steve]

AFAIU, there's something with the register numbers not right for the case,

+#if _MIPS_SIM==_ABIN32 || _MIPS_SIM==_ABI64 || _MIPS_SIM==_ABIEABI

but my MIPS-foo is limited to knowing "MIPS" some kind of acronym :-)
So I've added apinski to the conversation.

Ciao!
Steven

------------------------

I think I will add Richard Sandiford too.  I don't know why regdef.h in newlib would use the same register names for the EABI as for the N32 and 64 bit ABIs but there may be reasons I am not aware of.

I have reproduced the problem, I am going to try and rebuild after removing
'|| _MIPS_SIM==_ABIEABI' from regdef.h and see if things build once I have done that.

Steve Ellcey
sellcey@mips.com