Fix and clarify several cases of buggy boulder behaviour

Including #6900 - boulders reverting position after dispersal.

Then there were several cases where code assumed mons_is_projectile checked rolling boulder beetles, but in fact it didn't.
I added a monster::is_projectile() check which looks at both mons_is_projectile and mons_is_boulder, and called this
from the relevant places. Several times mons_is_projectile is actually just required for an IOOD check.

Also added support for catchup_move for boulders; previously they would be sat on the same square (not rolling) when you
returned to a level no matter how long you'd been gone. This was omitted from the original implementation.

1 files changed, 14 insertions, 10 deletions

diff --git a/crawl-ref/source/mon-project.cc b/crawl-ref/source/mon-project.cc
index cf8dcfe0d0..c8dbb0739b 100644
--- a/crawl-ref/source/mon-project.cc
+++ b/crawl-ref/source/mon-project.cc
@@ -605,21 +605,25 @@ static bool _iood_catchup_move(monster& mon)
 void iood_catchup(monster* mons, int pturns)
 {
     monster& mon = *mons;
-    ASSERT(mons_is_projectile(mon.type));
+    ASSERT(mon.is_projectile());
 
     const int moves = pturns * mon.speed / BASELINE_DELAY;
 
-    if (moves > 50)
+    // Handle some cases for IOOD only
+    if (mons_is_projectile(mons))
     {
-        _iood_stop(mon, false);
-        return;
-    }
+        if (moves > 50)
+        {
+            _iood_stop(mon, false);
+            return;
+        }
 
-    if (mon.props["iood_kc"].get_byte() == KC_YOU)
-    {
-        // Left player's vision.
-        _iood_stop(mon, false);
-        return;
+        if (mon.props["iood_kc"].get_byte() == KC_YOU)
+        {
+            // Left player's vision.
+            _iood_stop(mon, false);
+            return;
+        }
     }
 
     for (int i = 0; i < moves; ++i)