support asArray for sorting items - for buggins/dlangide#250

src/dlangui/core/collections.d

@@ -343,6 +343,13 @@ struct ObjectList(T) {
         }
         return res;
     }
+    /// Get items array slice. Don't try to resize it!
+    T[] asArray() {
+        if (!_count)
+            return null;
+        return _list[0.._count];
+    }
+    /// destructor destroys all items
     ~this() {
         clear();
     }