Changeset 403 for trunk/game/objects

Patch by Sirren & mvbarracuda:

• Added Sirren's gate from #224 to map.xml
• Note: it looks like there is no way around splitting up the pillars / walls of the gate into several tile-width (70*36px) pieces. Blocking can be done by adding invisible blockers but without splitting up the pillars into several smaller pieces, we'll always run into z-ordering issues.
• Please test it yourself, all feedback appreciated, if you got an idea how we could implement proper z-ordering without splitting up the pillars / walls, let us know