py/makeqstrdefs.py: Windows compatibility.

- msvc preprocessor output contains full paths with backslashes so the
  ':' and '\' characters needs to be erased from the paths as well
- use a regex for extraction of filenames from preprocessor output so it
  can handle both gcc and msvc preprocessor output, and spaces in paths
  (also thanks to a PR from @travnicekivo for part of that regex)
- os.rename will fail on windows if the destination file already exists,
  so simply attempt to delete that file first