TransferDbgValues (capital 'T') is wired into ReplaceAllUsesWith, and
transferDbgValues (lowercase 't') is used elsewhere (e.g in Legalize).
Both functions should be doing the exact same thing. This patch
consolidates the logic into one place.
Differential Revision: https://reviews.llvm.org/D40104
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318448 91177308-0d34-0410-b5e6-96231b3b80d8