Update x11-toolkits/ocaml-lablgtk2, unison to 2.51.3, fix depdent ports

[madpilot]

Summary

Latest unison requires a newer ocaml-lablgtk2. I updated the port.

I also backported fixes to older unison releases to make them compile against the newer ocaml-lablgtk2.

I'd like to commit this in one single atomic commit.

Test Plan

Build fine here in all supported realeses and run fine with unison.

[mandree]

Ho-hum, generally this looks good but now my point is I can't get unison232 to function (run-time), it tries to read its ~/.unison/default.prf, closes it, then prints 15 bytes of garbage to stderr and then SIGSEGV and the kernel disposes of it. FreeBSD 12.1-amd64.

No matter if I use current "latest" packages on 12.1, or if I rebuild lablgtk2 and unison232. unison232-text also crashes. I admit I haven't touched this code in years (minor edits to code in 2011 and 2013, and I no longer use it (or not 2.32 anyways). I made that port way back then because the new version had an incompatible net protocol. I don't know how to debug ML code... can't read it, don't know the tools. @madpilot would you have a look? Would you also be willing to maintain unison232? If so I'd be happy to transfer maintainership on this occasion.

[madpilot]

In D26924#600587, @mandree wrote:

Ho-hum, generally this looks good but now my point is I can't get unison232 to function (run-time), it tries to read its ~/.unison/default.prf, closes it, then prints 15 bytes of garbage to stderr and then SIGSEGV and the kernel disposes of it. FreeBSD 12.1-amd64.

Looking at the upstream repository I found a commit talking about fixes for ocaml 4.01. I'm posting it here for the record:

https://github.com/bcpierce00/unison/commit/891c081690ae4605c9bf818ee89fbdf2416b3dd7

Could be helpful in this case.

[mandree]

@madpilot for unison232, approved. Be sure to keep the changes from https://reviews.freebsd.org/rP553182 in your tree (i. e. update) before committing your patch.

[madpilot]

Going to update patch to cater for mandree changes and maybe import some improvements from mandree commit.

[madpilot]

Update diff to include refinements to the ports inspired by commit
from mandree:

Add a self test in post-build
remove MAKE_JOBS_UNSAFE

Also bumpe PORTREVISION on unison ports, I'm not sure they can
keep working if lablgtk is updated below them without being rebuilt.

[mandree]

In D26924#600684, @madpilot wrote:

Also bumpe PORTREVISION on unison ports, I'm not sure they can
keep working if lablgtk is updated below them without being rebuilt.

For unison 2.32, not required, I checked that explicitly, but I don't mind if you still do it for consistency, so feel free to leave it as proposed.

[mandree]

Approved of for net/unison232.