Teach InstCombineLoadCast about address spaces.

This is another one that doesn't matter much,
but uses the right GEP index types in the first
place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189854 91177308-0d34-0410-b5e6-96231b3b80d8
Fix grammar

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189855 91177308-0d34-0410-b5e6-96231b3b80d8