Revert Clang r172620 and r172629, which caused a hang when building
complicated modules (<rdar://problem/13038265>). Unfortunately, this
un-fixes <rdar://problem/13016031>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172783 91177308-0d34-0410-b5e6-96231b3b80d8