dh_python2: generates correct "python (<< 2.X)" dependencies for packages with private Python extensions

versions should be separated using comma, as in debian_defaults config file

(thanks to Mitsuya Shibata for the bug report)

(closes: #686358)

packages (Closes: #653741)

require.txt items that have a pydist file with (uscan like) rules
or PEP386 flag (Closes: #653740)

DEBPYTHON_SUPPORTED and DEBPYTHON_DEFAULT is used in tests instead

can be used to override list of supported/default Python versions in Debian

  - rewrite shebangs by default (disable via --no-shebang-rewrite),
    examples:
     + "/usr/bin/env python*" → "/usr/bin/python*"
     + "/usr/local/bin/python foo" → "/usr/bin/python foo"
     + "/usr/bin/python2" → "/usr/bin/python"
  - new --shebang option to replace all shebangs in bin dirs
    (example: --shebang /usr/bin/python2.6)

dh_python2: remove even more \.so.* dangling symlinks, thanks to Stefano Rivera for providing a test case

python2.7-minimal since python2.7 is not updated yet.

    python2.7-minimal
    - Add appropriage Breaks/Replaces

    - Describe addition of /usr/bin/python2 due to upstream changes
    - Remove redundant text on Python provides and clarify when they should be used
    - Update description of functionality related to X-Python-Version for Wheezy
    - Update X/XS-Python-Versions to also include X-Python-Version examples

    debian/idle.menu (Closes: #482156)

    (Closes: #657665)