Fix eternal drowning when NPC is thrown into deep water. (#3269)

* fix: NPCs no longer drown eternally after being thrown.

An NPC that was thrown into water would eternally drown, even after
getting back on land.

This also fixes that NPCs take damage from drowning normally while
being submerged in deep water after walking into it instead of being
thrown into it, which may not be a desirable change, since NPC
behaviour does not currently include a lot of deep water avoidance.

* fix: Disable NPCs taking damage from drowning.

src/npcmove.cpp

@@ -2461,6 +2461,7 @@ void npc::move_to( const tripoint &pt, bool no_bashing, std::set<tripoint> *nomo
     if( moved ) {
         const tripoint old_pos = pos();
         setpos( p );
+        set_underwater( g->m.is_divable( p ) );
         if( old_pos.x - p.x < 0 ) {
             facing = FD_RIGHT;
         } else {

src/suffer.cpp

@@ -253,7 +253,12 @@ void Character::suffer_while_underwater()
             mod_power_level( -bio_gills->power_trigger );
         } else {
             add_msg_if_player( m_bad, _( "You're drowning!" ) );
-            apply_damage( nullptr, bodypart_id( "torso" ), rng( 1, 4 ) );
+            // NPCs are not currently programmed to avoid or get out of deep water,
+            // so disable drowning damage for them.
+            // https://github.com/cataclysmbnteam/Cataclysm-BN/issues/3266
+            if( !is_npc() ) {
+                apply_damage( nullptr, bodypart_id( "torso" ), rng( 1, 4 ) );
+            }
         }
     }
     if( has_trait( trait_FRESHWATEROSMOSIS ) && !get_map().has_flag_ter( "SALT_WATER", pos() ) &&