Port tools to Python 3

This patch ports the utilities within the source package to Python 3. Most of this was accomplished simply by using the 2to3 utility.

Note that bin/asciidoc not ported as it is appears to be unused in the package build and there also is a Python 3 version available from upstream, so perhaps the embedded version can be removed at this stage.

 bin/cnvtblcols.py  | 36 ++++++++++++++++++------------------
 bin/colspec.py     |  8 ++++----
 debian/control     |  2 +-
 utils/asc2title.py |  4 ++--
 utils/moin2asc.py  | 32 ++++++++++++++++----------------
 utils/po4a-new.py  | 16 ++++++++--------
 utils/po4a-old.py  | 16 ++++++++--------
 utils/po4a-trim.py | 10 +++++-----

This MR sits on top of !5 (merged) meaning that you can see from CI that some of the scripts have been ported over to Python 3 successfully.

The actual packages appear to build correctly too.

Closes: #942942