Exploit spawning / ungarrisoning to climb impassable mountains

[elexis]

There are several ways how to get onto impassable mountains. All of them use a flaw when spawning units.

Example 1: Ungarrison units from a ship near a mountain. Example 2: Ungarrison units from a ram near a mountain. Example 3: Ungarrison units from a wall or houses that is build near a mountain. Example 4: Produce enough units at a barracks near a mountain. Build walls around the barracks or don't move the other correctly spawned to limit the area of newly spawned units.

Being on an impassable mountain has advantages like not being able to be defeated as the enemies can't attack you. Some nomad map types require units to go through a maze of impassable mountains. Thus being there allows you to kill the tradeline comfortably and even place towers there.

The flaw exists at least since alpha 18. The solution would be to check the height difference when spawning units. (Ungarrisoning probably uses the spawning algorithm too).

Bug reported and mastered by ffm.

[elexis]

Replay for r17126, provided by ffm.