Teach one piece of scalarrepl to handle lifetime markers. When transforming an

Teach one piece of scalarrepl to handle lifetime markers. When transforming an
alloca that only holds a copy of a global and we're going to replace the users
of the alloca with that global, just nuke the lifetime intrinsics. Part of
PR10121.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133905 91177308-0d34-0410-b5e6-96231b3b80d8