add_missing_frames: optimize.

* run after part insertion, within json_load/load_legacy functions
* push new frame into item list instead of using vehicle::install_part, which triggers
  find_external_parts, find_exhaust, precalc_mounts once for every frame added; load
  does this anyway.
* Only run if savegame_loading_version is v10 or below; new saves won't have vehicles
  with invalid frame config.

Author: atomicdryad

savegame_json.cpp

@@ -1431,6 +1431,11 @@ void vehicle::json_load(picojson::value & parsed, game * g ) {
         }
         parray = NULL;
     }
+    /* After loading, check if the vehicle is from the old rules and is missing
+     * frames. */
+    if ( savegame_loading_version < 11 ) {
+        add_missing_frames();
+    }
     find_external_parts ();
     find_exhaust ();
     insides_dirty = true;

savegame_legacy.cpp

@@ -1062,6 +1062,9 @@ void vehicle::load_legacy(std::ifstream &stin) {
         }
         parts.push_back (new_part);
     }
+    /* After loading, check if the vehicle is from the old rules and is missing
+     * frames. */
+    add_missing_frames();
     find_external_parts ();
     find_exhaust ();
     insides_dirty = true;

vehicle.cpp

@@ -78,11 +78,6 @@ void vehicle::load (std::ifstream &stin)
     } else {
         load_legacy(stin);
     }
-
-    /* After loading, check if the vehicle is from the old rules and is missing
-     * frames. */
-    add_missing_frames();
-
 }
 
 /** Checks all parts to see if frames are missing (as they might be when
@@ -108,7 +103,15 @@ void vehicle::add_missing_frames()
             }
             if(!found) {
                 //No frame here! Install one.
-                install_part(next_x, next_y, "frame_vertical", -1, true);
+                vehicle_part new_part;
+                new_part.id = "frame_vertical";
+                new_part.mount_dx = next_x;
+                new_part.mount_dy = next_y;
+                new_part.hp = vehicle_part_types["frame_vertical"].durability;
+                new_part.amount = 0;
+                new_part.blood = 0;
+                new_part.bigness = 0;
+                parts.push_back (new_part);
             }
         }