further updating contrib/debian

This should now build cleanly across ubuntu lucid/10.04+ and on debian/squeeze+

python-support will be used on lucid, and dh_sphinxdoc is not run on
distributions that have python-sphinx < 1.0.7+dfsg.  On older distributions
lacking dh_sphinxdoc, we manually install the documentation as needed and
attempt to patch up the same files as dh_sphinxdoc