BUG: Fix segfaults in ITKExamples

Added necessary compiler definitions for VTK factory mechanism in the
<module>_EXPORT_CODE_* variables to work. This fixes a segfault in
VisualizeStaticDense2DLevelSetAsElevationMapTest where no override was
found for vtkRenderer.

Change-Id: I8a4d438bbb56c5b4e725691bd3b35b3138d669b6
Merge topic 'fix_export_code_commands'

d7a9a31f BUG: Fix segfaults in ITKExamples