Updating PyQt version checks for v4.10+

[davidia]

pyqtconfig is deprecated:
http://pyqt.sourceforge.net/Docs/PyQt4/build_system.html

fixes #3021

[mdboom]

When was the new API added? How far back will the new code work? (We may need to keep both working for a period of time).

[jenshnielsen]

I have checked that the "new" API works on an RHEL 6 box with QT and PyQt based of version 4.6.2

[tacaswell]

I have failed to find an old version of the pyqt docs, but here: http://pyqt.sourceforge.net/Docs/PyQt4/qtcore.html#PYQT_VERSION_STR-var is the current docs. I would guess that something like that would be pretty stable and it is not listed in the possible incompatibility list. I suspect this is how we should have been doing it all along.