python: Improve Python detection.
python: Improve Python detection.

* m4/python.m4 (_AM_PYTHON_INTERPRETER_LIST): Prefer the generic
'pythonX' over 'pythonX.Y'.  This way we select the users preferred
version for both flavors.  Prefer 'python' over 'python3' but not over
'python2' so that the algorithm still finds a 'python2' even if
'python' is a Python3.

Fixes-commit: 5189c08af9468cdeb6f16a6ecd0fee53e1e3aa0e
Signed-off-by: Justus Winter <4d1bd7a5ca1cd26bee0df05b6801a6ce9a22196e@g10code.com>

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme