[PATCH] AArch64: Fold immediate into the immediate field of logical instructions

[Akira Hatanaka]

I had to make changes to DAGCombiner::visitAND because it was transforming the DAG in way that made it impossible to do any optimization in optimizeConstant (the code here was originally committed in r97616). This change doesn't seem to have any noticeable impact on performance, but I'm still investigating.

http://reviews.llvm.org/D5591