Some tweaks to gamecode.
Cheat fixes:
-------------
Don't reset health to max if more than max already.
Don't give ammo to grappling hook/gauntlet with give ammo.
Team Arena: Don't allow give armor with scout.
Add quick 100s powerup cheats: quad, haste, invis, fly, regen, suit
Fix 2 potential null derefs when giving items.
-------------
Fix old team check when doing /team for timer to only happen if a team change actually happened.
Prevent switching to spectator via follow cmds getting around the team change timer.
Don't allow switching teams in single player.
Don't drop ammo back down to 200 if already above 200 (give ammo)
Also set ammo to -1 if some mapper puts a gauntlet in.
Team Arena: Null deref check on health pickups with guard.
Team Arena: Don't trigger your own mines.
Team Arena: Don't play juiced event on proxmine internal detonation if they didn't actually die. (god/powerup)