JamTaba build fails with Qt5.15

[kdoren]

Qt 5.15 (used in Debian bullseye) requires explicit #include for QPainterPath.

This causes JamTaba build to fail.
see: https://wiki.debian.org/qa.debian.org/FTBFS

I made a PR which fixes this. This PR allows building under Qt5.15 but still allows building under earlier Qt 5.11.
#1412