Add back undefining _POSIX_C_SOURCE and _XOPEN_SOURCE (MeVisLab#106)

- only undefining _POSIX_THREADS had be a problem
- see MeVisLab#103

Limit string representation of argument list in length

otherwise when passing image data to the QImage constructor this can get rather long

CI for CONFIG+=debug + UbSan for tests

Fix UBSAN error for invalid access through pointer. This happens only for Python2 because Py_DECREF is slightly different. Still, I have no opinion if UBSAN is right or wrong here, but this problem occures with the latest XCode/clang available too.

Add missing break in switch to fix P3K conversion

for QVariant::ByteArray

renamed to 3.2

created branch

branch for 2.1

creating release branch