Support multiple python versions in brp-python-bytecompile (RhBug:53117)

Support multiple python versions in brp-python-bytecompile (RhBug:53117)
- For *.py files in python library path, use matching python interpreter
  version for compiling, this is especially needed for Python 3 which
  is very different from Python 2 code. And even if the code compiled
  with a wrong version, it would be recompiled at run-time when invoked
  with the intended python version, causing verification errors etc.
- For *.py files outside the library path, use "system python" which
  might not be always correct but we dont really know any better.
- Patch from David Malcolm