Fix 'debug_file' in PESourceLineWriter.

- Add a #define to testing.gyp to avoid warnings about TR1 deprecation.
- PESourceLineWriter now reads debug_file from CodeView record instead
  of using code_file value.
- Updated PE-only MD reading unit test.

Change-Id: Ib4e6201df3e3fd651e160f310584b5a67b16c842
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/1668347
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>