[vtkusers] vtkFLTK building problems

[Alberto Orlandini]

I finally managed to build everything!

I just tried different combinations of the projects' 
versions... this one worked for me:

vtk 5.0
fltk 1.1.7
vtkfltk 0.6.1

I used cmake 2.6 to build vtk and fltk for VS9 2008, then I 
removed the #warning preprocessor directive which was not 
supported by MSVS, I included <windows.h> to solve problems 
about redefinitions of functions like GetClassName into 
GetClassNameA, and I finally downloaded the full opengl 
includes and libs from microsoft.com and it worked