Replace libsignal-protocol-c with libomemo-c

[jubalh]

The library libsignal-protocol-c is not maintained. This commit will replace the dependency libsignal-protocol-c with libomemo-c.

On 2025-02-07 a new version of protobuf-c has been uploaded to Debian. This new version induced a bug for libsignal-protocol-c and libomemo-c:

• Bug#1095352: libomemo-c: FTBFS [1]
• Bug#1095353: libsignal-protocol-c: FTBFS [2]

(Thanks to Dino team and Debian Maintainer it's solved)

libomemo-c [3] is a fork of libsignal-protocol-c [4] maintained by the Dino team.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1095352
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1095353
[3] https://github.com/dino/libomemo-c
[4] https://github.com/signalapp/libsignal-protocol-c

Note:
Commits squashed and commit message edited by @jubalh.

[jubalh]

Received those patches via PM and mailinglist from Stefan.

Comments (to Stefan):
I squashed the two commits into 1. If you use 2 commits then the configure change should have been done with the same commit as changing the source files. Since otherwise it wouldn't build ;)
Then the CI changes could be a separate step.

Don't forget that we use present tense in commit messages (Replace not Replaced).

I also added the (quite valuable) info that you added to the email but not to the patch files themselves.

And CI sais no :)

[Neustradamus]

@jubalh: Nice! :)

Can you help to update libomemo-c to latest XEP-0384 version?

• https://xmpp.org/extensions/xep-0384.html

At this time: 0.8.3 (2022-01-18).

Ticket here:

• XEP-0384: OMEMO Encryption support update dino/libomemo-c#11

Note: @Ri0n from @psi-im team has done a PR here:

• Various cmake improvements dino/libomemo-c#10

[jubalh]

@sjaeckel do we want an ifdef or just switch to libomemo-c?