PerformBFICombine - (bfi A, (and B, Mask1), Mask2) -> (bfi A, B, Mask2) iff

the bits being cleared by the AND are not demanded by the BFI.

The previous BFI dag combine rule was actually incorrect (or used to be
correct until BFI representation changed).

rdar://9609030

llvm-svn: 133034