libmodulemd: SOname bump coming to released Fedora

[Stephen Gallagher]

I'm going to be submitting an update for libmodulemd today for all released
branches of Fedora. This is *technically* in conflict with the Stable
Updates Policy, but it is both necessary and should be safe to accomplish.

1) The teams that were planning to switch to it from the previous
python-modulemd have not yet done so or are just starting to, so it's not
believed there is anything currently running in production with the older
version.
2) The API is *source*-compatible, but not binary-compatible (hence the
soname bump), so it will just require a rebuild if anyone *is* using it.
3) The reason for the API change is that certain semantics around ownership
of memory have changed. This mostly impacts the GObject Introspection
bindings for other languages such as Python, but as it technically changes
the ABI contract, bumping soname was the correct thing to do.

[f26] https://bodhi.fedoraproject.org/updates/FEDORA-2018-f731883394
[f27] https://bodhi.fedoraproject.org/updates/FEDORA-2018-a1c9076f1f