FIX: {} were missing around FLTK_*_LIBRARY.

Modules/FindFLTK.cmake

@@ -54,7 +54,7 @@ IF(FLTK_INCLUDE_PATH)
     )
   ENDIF(USE_FLTK_VERSION_1.1)
 
-  SET( FLTK_LIBRARY $FLTK_BASE_LIBRARY $FLTK_GL_LIBRARY $FLTK_FORMS_LIBRARY )
+  SET( FLTK_LIBRARY ${FLTK_BASE_LIBRARY} ${FLTK_GL_LIBRARY} ${FLTK_FORMS_LIBRARY} )
 
 ENDIF(FLTK_INCLUDE_PATH)