Use the expansion location of the file name when finding the module.

The spelling location of stringified strings is not a file location.
Optimally, we'll want to solve the problem (as the FIXME states) by
handing in the right FileEntry of the #include location.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204220 91177308-0d34-0410-b5e6-96231b3b80d8