Header hygiene: remove using directive and #undef DEBUG_TYPE once we're done.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214263 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "UseListOrder: Remove move assignment"

This reverts commit r214260.  Turns out move assignment *is* necessary
for MSVC [1].

[1]: http://bb.pgr.jp/builders/ninja-clang-i686-msc17-R/builds/9631

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214264 91177308-0d34-0410-b5e6-96231b3b80d8