I should have changed meta.branch in 70e33e3ae3 ("glsurf: use current giflib"),
but I overlooked it.
The bitbucket URL doesn't seem to exist any more, so I've updated the
homepage to the GitLab repository we fetch the sources from.
Fixes: 70e33e3ae3 ("glsurf: use current giflib")
This requires bumping the version of camlimages used by glsurf to a
version that supports current giflib. The most recent versions of
camlimages (even of 4.x) don't support ocaml 4.01 any more, so I've
upgraded to 4.1.2 here, the last version that supports ocaml 4.01 (and
which happily supports current giflib).
