Unfortunately, since the "EXPAND_ONLY_PREDEF" Doxygen option is being
used, all preprocessor macros must be explicitly redefined in
doxyfile.in. This commit updates the redefinition for vtkTypeMacro.

Additionally, update the documentation string for GetClassName().

Change-Id: I8313e0b3602514c48ac16d6e246ade5549036b1f