DomTreeUpdater depends on headers from Analysis, but is in IR. This is a
layering violation since Analysis depends on IR. Relocate this code from IR
to Analysis to fix the layering violation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353265 91177308-0d34-0410-b5e6-96231b3b80d8
