Fix getNode to allow a vector for the shift amount for shifts of vectors.

Fix getNode to allow a vector for the shift amount for shifts of vectors.
Fix the shift amount when unrolling a vector shift into scalar shifts.
Fix problem in getShuffleScalarElt where it assumes that the input of
a bit convert must be a vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60740 91177308-0d34-0410-b5e6-96231b3b80d8