08a79be4 Add a missing PyGILState_Ensure for matplotlib
a0c96aa6 VTK_UNBLOCKTHREADS hint to unblock Python threads
5df65311 Add VTK_PYTHON_FULL_THREADSAFE as option

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Acked-by: Marc Greuter <m.alexander.greuter@gmail.com>
Acked-by: Christos Tsolakis <christos.tsolakis@kitware.com>
Merge-request: !9223