Node arguments to type casts can have names too. This code

needs to be majorly refactored, but this spot bugfix allows
things like:

 def vmrghw_shuffle : PatFrag<(ops node:$lhs, node:$rhs),
                             (vector_shuffle (v4i32 node:$lhs), node:$rhs), [{
...

llvm-svn: 97952