liblogging-1.0.2 should also check for rst2man.py

Hi,

the current liblogging-1.0.2 configure script only checks for ```rst2man```. But if you install the Python docutils packages via PiP or from PyPi you will end with ```/usr/bin/rst2man.py``` instead of ```/usr/bin/rst2man``` so you should support both.

PS: That you are now using rst2man (docutils dependency; yes optional - you could use the cached version) is something I would have mentioned in the changelogs, too.