ocaml-lablgtk2.mk : extra dependency w.r.t. gtksourceview

Hi
Since gtksourceview is already available as an mxe package, we could enable its support in ocaml-lablgtk2.
We just have to declare it as an extra dependency : the ./configure script of lablgtk2 will then do the right autodetection. This will help cross-compiling the coq software (coq.inria.fr).
Thanks!
Pierre Letouzey