[vtkusers] vtkFLTK major update

[Sean McInerney]

The 0.4 release of vtkFLTK primarily addresses incompatibilities with 
the changes in FLTK's OpenGL context handling introduced in FLTK 1.1.4.
vtkFLTK 0.4.1 adds improvements to the CMake build configuration as well 
as some minimal documentation regarding the build process.

URL: http://vtkfltk.sourceforge.net/