[Cmake] Bug in FindFLTK.cmake

[Brad King]

> A small omission in this file (version 1.6 release of CMake) is that it
> searches for FLTK libraries in
>
> /usr/local/fltk/lib
>
> but not in
>
> /usr/local/lib/fltk
>
> which where I assume most people would install fltk

Thanks.  I've fixed it in CVS.  I think the next version of cmake will
have a totally new implementation (perhaps using fltk-config).

-Brad