Deprecate use of <Collide> without specifying "descend" flag

panda/src/doc/eggSyntax.txt

@@ -1476,6 +1476,10 @@ GROUPING ENTRIES
     its geometry is used to define the extent of the collision
     surface (unless the "descend" flag is given; see below).
 
+    It is now deprecated to use <Collide> without "descend"; it will
+    become the default soon.  You should always specify it for best
+    compatibility.
+
     Valid types so far are:
 
     Plane
@@ -1538,11 +1542,12 @@ GROUPING ENTRIES
 
     descend
 
-      Instead of creating only one collision object of the given type,
-      each group descended from this node that contains geometry will
+      Each group descended from this node that contains geometry will
       define a new collision object of the given type.  The event
       name, if any, will also be inherited from the top node and
-      shared among all the collision objects.
+      shared among all the collision objects.  This option will soon
+      be the default; it is suggested that it is always specified for
+      most compatibility.
 
     keep
  

panda/src/egg2pg/eggLoader.cxx

@@ -2970,6 +2970,10 @@ make_collision_solids(EggGroup *start_group, EggGroup *egg_group,
         make_collision_solids(start_group, DCAST(EggGroup, *ci), cnode);
       }
     }
+  } else {
+    egg2pg_cat.warning()
+      << "Using <Collide> without 'descend' is deprecated.  'descend' "
+      << "will become the default in a future version of Panda3D.\n";
   }
 }