Revert "Remove the deprecated PYTHON_INCLUDE_PATH variable."

This reverts commit 698f17d64b093db488de7d5ef33a8c15adfe8765.
The deprecated PYTHON_INCLUDE_PATH variable was still being
used by Wrapping/Python/CMakeLists.txt.

Change-Id: I3e9e433b974ffbbf38f5a546a95b526ccfda2581
Merge topic 'python-version-match' into master

530bc43e Revert "Remove the deprecated PYTHON_INCLUDE_PATH variable."
COMP: Missing type for vtkWindow GetScreenSize()

Change-Id: Iad4ac1a190b4582afead46b88b39f2517a0ca5d4
Merge topic 'Fix-WrapHint' into master

e34f6f61 COMP: Missing type for vtkWindow GetScreenSize()
Remove obsolete PYTHON_INCLUDE_PATH from CMakeLists.

Change-Id: Iad8a7d033b74e558b6a4e9692fdf851bf711c637
Merge topic 'obsolete-python-include-path' into master

18e5fa23 Remove obsolete PYTHON_INCLUDE_PATH from CMakeLists.