Add support for ffmpeg 6.0 - Use the new send_frame/receive_packet API for encoding - Use the new channel layout API for audio - Fix audio recording - Copy codec parameters to the stream parameters - Set correct pts for audio frames - Read audio samples from file directly to the refcounted AVFrame buffer instead of the `g_pSamples` buffer - Use global AVPackets allocated with `av_packet_alloc` - Stop trying to write more audio frames when `WriteAudioFrame` fails with a negative error code - Fix segfault with `g_pContainer->url`. The field has to be allocated with `av_malloc` before writing to it. It's set to `NULL` by default. - Properly free allocations with `avcodec_free_context` and `avformat_free_context`

1. Fix broken trainings/missions
2. Update translations (check fireforge for patches)
3. Check copyright headers
4. Changelog
5. Turn debug stuff off (frontend console output)
6. Update message in game server, update check for client version
7. Make a branch
8. Make packages
9. Test packages
10. Upload (hedgewars.org, fireforge.net, gna.org (rsync --delete  -avr --rsh="ssh" . unc0rr@download.gna.org:/upload/hedgewars))
11. Post news (hedgewars.org, hedgewars forum, fireforge.net, gna.org, happypenguin, etc.)
12. Make tag (svn copy svn+ssh://unc0rr@svn.fireforge.net/svnroot/hedgewars/branches/0.9.7 svn+ssh://unc0rr@svn.fireforge.net/svnroot/hedgewars/tags/0.9.7 -m "Tag for 0.9.7 release")