refactor: use squared distance if possible

refactor: add some const-correctness to code

src/linkage.cpp

@@ -115,7 +115,7 @@ CR_EXPORT int GetEntityAPI (gamefuncs_t *table, int) {
       if (!game.isNullEntity (pentTouched) && pentOther != game.getStartEntity ()) {
          auto bot = bots[pentTouched];
 
-         if (bot && game.isShootableBreakable (pentOther)) {
+         if (bot && util.isShootableBreakable (pentOther)) {
             bot->checkBreakable (pentOther);
          }
       }