package/fltk: bump to 1.3.3

In this release two dependencies on xlib_libXcursor
and xlib_libXfixes have been added.

See http://www.fltk.org/articles.php?L1392



Also add hash file

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>