[PATCH] [Reassocate] Add support for vector instructions.

[Sanjay Patel]

On closer inspection, -instcombine is handling all of the transforms in the fmul testcases that I added in the other patch, so the changes to -reassociate with this patch aren't coming into play at all...but only if 'fast' is specified on each fmul; the function attribute appears to be ignored.

http://reviews.llvm.org/D5222