Avoid ‘bad corpseNum’ errors.

This is caused by spectating bots (bots branch) being killed.

I noticed that buildings such as the overmind continued ‘attacking’ even
though the bot(s) near it had been moved to spectators. Marking the entity
as not taking damage when spectating fixed that, but then the attack resumed
as soon as it was put back on the human team until it was respawned.

Solution: allow damage to be taken only when on a team and not spectating.
Don't allow extend votes when there is no time limit.

Otherwise the game time could be set to 10 minutes – and if 10 minutes have
already elapsed since start, game over.
Avoid localisation issues with md5sum in the download script.

(Fixes issue 150)
Use ambient and directional light for /r_rimLighting mode
Have /setlevel use admin_find_admin().
Bump the buffer size for the GL info text to 32000 bytes.
Clean up admin print, fixing remaining quoting issues.
Merge branch 'master' into training