Steve Cotton 551357f48b Fix an off-by-one in mapgen's x and y filters, and add unit tests
Fixes the currently suspected root cause of #5108, but requires further testing
to confirm that it fixes that issue.

Closes #6501 (the question of how to test the mapgen filter).

(cherry picked from commit 30f50bac681fda1566f5cee5aad7be6b65cb0fdb)
2021-09-01 15:48:32 +02:00
..