Fortress random map bugfixes and cleanup.

Fix typo in rP21073 reported by mimo.
Replace magic trigonometric equation from rP13622 with a createArea call to the polygon placer from rP21082 to draw the fortress texture on an arbitrarily rotated square.
Fix wrong treasure distance in rP20882.
Remove treasure self-avoidance in rP11361, since it can result in the treasure not being placed.