Revert "DebugInfo: Don't include the name of the CU file in the line table file list when it's unneeded"

This reverts commit r201380 for now while we investigate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201389 91177308-0d34-0410-b5e6-96231b3b80d8