Bug#1003837: Acknowledgement (client gets stuck with high CPU load)

[Harald Dunkel]

Apparently this has bee triggered by the upgrade of libsd2-2.0-0. If I downgrade
this package to the version in stable, the bzflag works again.

```
Aptitude 0.8.13: log report
Sun, Jan 23 2022 17:40:07 +0100

   IMPORTANT: this log only lists intended actions; actions which fail
   due to dpkg problems may not be completed.

Will install 1 packages, and remove 2 packages.
211 kB of disk space will be freed
========================================
[REMOVE, NOT USED] libdecor-0-0:amd64 0.1.0-3
[REMOVE, NOT USED] libdecor-0-plugin-1-cairo:amd64 0.1.0-3
[DOWNGRADE] libsdl2-2.0-0:amd64 2.0.20+dfsg-2 -> 2.0.14+dfsg2-3
========================================

Log complete.
```