Bug#802919: unison: synchronization incompatibility when built with Ocaml versions pre/post-4.02

[Baptiste Jonglez <baptiste@bitsofnetworks.org>]

As a side note, the current state of unison/ocaml on stretch is confusing:
ocaml 4.02.3 is in stretch, but the unison binary package still seems to
be built against ocaml 4.01.  This is non-obvious and I spent quite some
time wondering why unison from stretch did not interoperate with another
unison client built against ocaml 4.02.

Of course, rebuilding the unison package against ocaml 4.02 would break
compatibility because of the bigarray change, so this is most likely not
acceptable...

As a workaround, would it be possible to keep this unison package
unchanged (built against ocaml 4.01), and add a new package
unison-ocaml4.02 built against the new ocaml?

Thanks,
Baptiste