remmina-plugin-rdp has undeclared dependency on non-existing libavcodec-ffmpeg-extra56

[Åsmund Grammeltvedt]

remmina-plugin-rdp installs fine, but doesn't actually load on bionic, due to a missing dependency on libavcodec-ffmpeg-extra56:

» cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.1 LTS"

» remmina --version
Failed to load plugin: /usr/lib/x86_64-linux-gnu/remmina/plugins/remmina-plugin-rdp.so.
Error: libavcodec-ffmpeg.so.56: cannot open shared object file: No such file or directory
StatusNotifier/Appindicator support: your desktop does support it and libappindicator is compiled in remmina. Good!
Running under Gnome Shell version 3.28.3
Remmina - 1.2.0-rcgit-29 (git rcgit-29)

» dpkg -l remmina-plugin-rdp
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-========================-=================-=================-=====================================================
ii remmina-plugin-rdp:amd64 1.2.0-rcgit.29+df amd64 RDP plugin for Remmina

libavcodec-ffmpeg.so.56 used to be provided by libavcodec-ffmpeg-extra56, but this has been removed in bionic.