SCEVExpander fix. RAUW needs to update the InsertedExpressions cache.

Note that this bug is only exposed because LTO fails to use TTI.

Fixes self-LTO of clang. rdar://13007381.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172462 91177308-0d34-0410-b5e6-96231b3b80d8