Log Message:
Bug fixes for the 1.2 release.

Engine changes
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* Fix entity:is_in_same_region() giving wrong results
* Fix custom_entity:set_can_traverse() giving opposite results.
* Fix custom_entity:on_interaction() not always called.
* Fix custom_entity sprite collision issues with some entities
* Fix a crash in enemy:restart() when the enemy is dying
* Fix hero:set_tunic_sprite_id() resetting the direction to right
* Fix timer:get_remaining_time() always returning 0
* Fix declaring global variables from a map script
* Fix the hero sometimes moving while no keys are pressed
* Fix on_joypad events not always working
* Add an error when a hero sprite animation is missing

Solarus Quest Editor changes
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* Fix corrupted image in quest created by Quest > New quest
* Fix tiles created on invisible layer
* Fix crash when an NPC sprite does not have 4 directions