Find the native FLTK2 includes and library
The following settings are defined
FLTK2_FLUID_EXECUTABLE, where to find the Fluid tool FLTK2_WRAP_UI, This enables the FLTK2_WRAP_UI command FLTK2_INCLUDE_DIR, where to find include files FLTK2_LIBRARIES, list of fltk2 libraries FLTK2_FOUND, Don't use FLTK2 if false.
The following settings should not be used in general.
FLTK2_BASE_LIBRARY = the full path to fltk2.lib FLTK2_GL_LIBRARY = the full path to fltk2_gl.lib FLTK2_IMAGES_LIBRARY = the full path to fltk2_images.lib