Refactor python snippets: Handle flavors (not versions).
Rename cdbs_python2_builddeps → cdbs_python_builddeps_python2, and deprecate the former.
Rename cdbs_python3_builddeps → cdbs_python_builddeps_python3, and deprecate the former.
Refactor python snippets: Check actual need for build-dependencies in cdbs_python_builddeps (not before).
Refactor python snippets: Expand packaging systems from list.
Refactor python snippets: Handle runtimes separate from flavors.
Support building python modules for pypy

CDBS will trigger build of python module for pypy, if it finds pypy-
prefix in binary package name. This patch tries to be compatible with
existing tasks done by CDBS for python and python3 variants where ever
it is possible.
Drop unused (according to <http://codesearch.debian.net>) snippets docbookxml.mk hbuild.mk kde.mk.
Update autotools (with autoreconf -f -i).
Add myself to Uploaders
Fix have perl-build.mk more aggressively detect use of Module::Build::Tiny.
Drop variables deprecated for ages and unused (according to codesearch.debian.net): cdbs_python_selected_pyversions DEB_DH_INSTALL_MENU_ARGS DEB_DH_INSTALLDEBCONF_ARGS DEB_DH_INSTALLCATALOGS_ARGS DEB_DH_INSTALLLOGROTATE_ARGS DEB_DH_INSTALLDEB_ARGS DEB_DH_LINTIAN_ARGS.
Rephrase python-module.mk warning to mention multiple python systems (not python2 and python3 specifically).
Add FIXMEs and TODOs.