Broken OBS builds

I noticed some breakage in the OBS builds of Purr Data, due to recent changes in dependencies. I'm currently working on fixing these, so expect an MR soon when I'm done testing my changes.

• Debian/Ubuntu: libdc1394-22-dev was renamed to libdc1394-dev, and libgmerlin was updated from 1.2 to 2.0 in Ubuntu 22.04. The former is easily fixed in the debian/rules file, but the latter causes a compile error in Gem's filmGMERLIN module. My proposed solution is to just remove the Gmerlin dependency. It isn't really needed any more, as we also support video playback via the Quicktime backend (in fact, I removed the Gmerlin dependency from the Arch build already in 2018, and I didn't notice any bad effects there).

• Arch: libquicktime was moved from the official repositories to the AUR (Arch User Repositories). This doesn't affect the AUR build, as libquicktime is still available there, but it will affect the OBS build. The only solution I see right now is to just remove the dependency on libquicktime in the OBS PKGBUILD, which might adversely affect the user experience when trying to play back some video formats which are only supported in the Quicktime backend. (Users can always work around this if needed by just building Purr Data themselves using the AUR package.)

NB: In the long run, this probably means that we will have to update Gem once more to hopefully get better video backend support which doesn't rely on libquicktime (the upstream libquicktime project hasn't been maintained in a long time and thus seems pretty much dead now).