Added checking code whehter target supports specific dag combining about rotate

Added checking code whehter target supports specific dag combining about rotate
or not. The corresponding dag patterns are as following:

"DAGCombier::MatchRotate" function in DAGCombiner.cpp
Pattern1
// fold (or (shl (*ext x), (*ext y)),
//          (srl (*ext x), (*ext (sub 32, y)))) ->
//   (*ext (rotl x, y))
// fold (or (shl (*ext x), (*ext y)),
//          (srl (*ext x), (*ext (sub 32, y)))) ->
//   (*ext (rotr x, (sub 32, y)))

pattern2
// fold (or (shl (*ext x), (*ext (sub 32, y))),
//          (srl (*ext x), (*ext y))) ->
//   (*ext (rotl x, y))
// fold (or (shl (*ext x), (*ext (sub 32, y))),
//          (srl (*ext x), (*ext y))) ->
//   (*ext (rotr x, (sub 32, y)))

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191905 91177308-0d34-0410-b5e6-96231b3b80d8