Update: just bugfixes today

What's new:

• Bugfix: safe zone head jumps still counted as kills (even though no actual kill happened).
• Bugfix: players were able to bounce on top of other players in safe zones or while the "victim" is in placement mode.
• Bugfix: mines exploded in placement mode if they were moved over a safe zone; now they only explode in safe zones after they have been placed on the level.
• Bugfix: mines/sawblades placed right over NPCs didn't kill them (they were tested for collision, not for overlapping)