New map/forest tool spawns quarter forests

[Leartin]

Trees only get planted in one quadrant of the area supposed to be a forest.
Reason: The check to avoid placement outside the map edge compares to a position relative to the forest center, rather than an absolute position of the map. Hence 3/4 are 'outside the map'.

Fix attached.

[makie]

yes, this bug has also bothered me

thank you for searching

[prissi]

Thank you, in in r9561.