Also clear items in clear_map

Failing to do so could break the crafting tests because extra items
might be available for crafting nearby, thus causing the crafting code
to need to ask the player which one to use (which triggers UI code which
aborts in test mode, since there's no UI).

tests/map_helpers.cpp

@@ -76,6 +76,16 @@ void clear_fields( const int zlevel )
     }
 }
 
+void clear_items( const int zlevel )
+{
+    const int mapsize = g->m.getmapsize() * SEEX;
+    for( int x = 0; x < mapsize; ++x ) {
+        for( int y = 0; y < mapsize; ++y ) {
+            g->m.i_clear( { x, y, zlevel } );
+        }
+    }
+}
+
 void clear_map()
 {
     // Clearing all z-levels is rather slow, so just clear the ones I know the
@@ -87,6 +97,9 @@ void clear_map()
     clear_npcs();
     clear_creatures();
     g->m.clear_traps();
+    for( int z = -2; z <= 0; ++z ) {
+        clear_items( z );
+    }
 }
 
 void clear_map_and_put_player_underground()

tests/map_helpers.h

@@ -13,6 +13,7 @@ void wipe_map_terrain();
 void clear_creatures();
 void clear_npcs();
 void clear_fields( int zlevel );
+void clear_items( int zlevel );
 void clear_map();
 void clear_map_and_put_player_underground();
 monster &spawn_test_monster( const std::string &monster_type, const tripoint &start );