Port API coverage reporting to Python 3 and adapt to current doxygen output

alsa-project/alsa-python pull request #15 was opened from tormodvolden:

Tested by comparing the new output from alsa-python-coverage.py with the old COVERAGE file.

For transparency and easier review there are multiple commits for the Python 3 fixups, but this can be squashed if desired.

Request URL : https://github.com/alsa-project/alsa-python/pull/15 Patch URL : https://github.com/alsa-project/alsa-python/pull/15.patch Repository URL: https://github.com/alsa-project/alsa-python