Fix MSG_ReadDeltaKey setting bit 1<<bits often

MSG_ReadDeltaKey would often set 1<<bits, it should never be set. It exceeds the size of what was being read.
Worked okay for weapons/forward/right/up as they stored as chars (value would wrap around to correct value, lucky).
Angles had the wrong value, not sure if it was causing issues.
Remove some unused defines from msg.c
Use Q_strncpyz in G_AddRandomBot
Remove MSG_WriteDeltaUsercmd and MSG_ReadDeltaUsercmd
Merge Reaction renderer features, remove "#ifdef REACTION"s
Merge branch 'reactionmerge'