Trouble with opam install glMlite

While on the topic of opam packages, there's another one I'm having 
trouble with.  A few years ago I wrote a very simple video game in 
response to a challenge.  I decided to do it in OCaml using glMlite, 
which I obtained in source form.  Now glMlite is now an opam package, 
and I thought I should simplify things for any potential users (in the 
vain hope that there might actually be one - the game only amuses me for 
about ten minutes before I tire of it) by using the opam package.

Alas! it fails:

hendrik@notlookedfor:~/dv/fun/wander$ make wander
ocamlfind ocamlopt -package glMLite -package unix -linkpkg wander.ml -o 
wander
File "wander.ml", line 652, characters 6-25:
Error: Unbound module Png_loader
Makefile:5: recipe for target 'wander' failed
make: *** [wander] Error 2
hendrik@notlookedfor:~/dv/fun/wander$ 

The module Png_loader is missing from opam's glMlite.  Now the Makefile 
for glMlite contains some options that specify which modules are to be 
built.  Some of these modules are bindings to libraries that most 
users are unlikely to have or want.  And compiling these modules seems 
to require that those libraries present.  I know I had to use aptitude 
to install them before I could build everything. 

But Png_loader is not generated in opam's glMlite.

Is there a way on the opam install commnd to specify the missing option?

and, if I should ever get around to packaging this game, is there any 
way to specify I need these options in its dependencies?

-- hendrik