Fix new lang/ocaml port missing camlp4 and labltk (bug 199845)

[madpilot]

Summary

As described in bug 199845 here:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199845

the new ocaml distribution sheds some parts, which are now separate projects.

This patch modifies Mk/bsd.ocaml.mk to add some USE_ flags to cater for those extensions and fixes dependent ports.

Please note that this patch requires bugs 195737 199895 to be committed first.

Test Plan

If needed I'll request an exp-run for all ports depending on ocaml. I am running such a test myself on my machine.

Anyway most of the touched parts are already broken at present.

[madpilot]

I forgot to mention that the following ports:

net-p2p/mldonkey-*
www/ocaml-net

are failing with unrelated errors (unterminated string literal) which I don't address here.

I think it's fallout from some other change in ocaml.

[madpilot]

New patch which also updates graphics/ocaml-lablgl x11-toolkits/ocaml-lablgtk2 to the latest versions.

There is this bug reported upstream:

https://forge.ocamlcore.org/tracker/index.php?func=detail&aid=1425&group_id=220&atid=1033

which shows up, I'm preparing a further patch including the fix from upstream.

[madpilot]

Previous patch contained a wrong update to lablgtk2.

This patch really updates x11-toolkits/ocaml-lablgtk2.

Ports depending on lalblgtk2 need to be rebuilt, so I bumped their portrevisions.
I also modified the unison ports (which I maintain or have implicit approval on) to use the USE_OCAML flags instead of BUILD/RUN_DEPENDS.

[mat]

[madpilot]

Changes committed.