Remember to track spill slot uses in VirtRegMap when inserting loads and stores.

Remember to track spill slot uses in VirtRegMap when inserting loads and stores.
LocalRewriter::runOnMachineFunction uses this information to mark dead spill
slots.

This means that InlineSpiller now also works for functions that spill.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107302 91177308-0d34-0410-b5e6-96231b3b80d8