Add routines for temporary terrain manipulation

Each terrain change specifies a desired feature, a duration (which may
be INFINITE_DURATION), a terrain change type (used for reference and
stacking at the moment), and optionally a source monster (if one is
specified, the terrain change is undone upon the monster's death)

A temporary terrain change will automatically revert to the original
underlying feature when it times out, or the source monster is killed.

There can only be one terrain change of a given type at a single
location. A new change of the same type will overwrite the old one
if it either changes the terrain to a different feature type than the
old one, or has a greater duration than remains of the old one (this
will change the associated source monster, if appropriate).

1 files changed, 2 insertions, 0 deletions

diff --git a/crawl-ref/source/misc.h b/crawl-ref/source/misc.h
index 36e27ee9d4..af0d969264 100644
--- a/crawl-ref/source/misc.h
+++ b/crawl-ref/source/misc.h
@@ -92,6 +92,8 @@ void timeout_malign_gateways(int duration);
 
 void timeout_door_seals(int duration, bool force = false);
 
+void timeout_terrain_changes(int duration, bool force = false);
+
 void setup_environment_effects();
 
 // Lava smokes, swamp water mists.