altivec: mov patterns, add m<-r and r<-r

[David Edelsohn]

>>>>> Aldy Hernandez writes:

Aldy> uhh, duh.  maybe i should steal the rest of the code as well ;-).
Aldy> will the above work with overlapping registers?

	That's the point of the two cases.  GCC allocates TImode with
sequential registers.  I assume vector modes overlayed on GPRs as well.
If there is overlap, it will be at one end or the other, so one simply
needs to do the move in the order that is non-destructive. 

David