Disable python signal handlers in matplotlib module.

Change-Id: I891ef3ffa16aef481feb32949c78b2a9b113e9b2
Merge remote-tracking branch 'origin/master' into HEAD

Conflicts:
	Rendering/Matplotlib/vtkMatplotlibMathTextUtilities.cxx

Change-Id: I8c30e9852c1d819c1bb2fd0d75b6517742305cb7
Merge topic '13788-FixSignalHandlers' into master

4db96685 Merge remote-tracking branch 'origin/master' into HEAD
7ca26385 Disable python signal handlers in matplotlib module.