[tests] Add regression test for int *= overflow

Author: tobil4sk

test/cppia/Client.hx

@@ -197,6 +197,14 @@ class Client
          return;
       }
 
+      // regression test for #1257
+      var x = 1290555;
+      x *= 1290555;
+      if (x != -915102823) {
+         Common.status = 'Failed regression test for #1257. x: $x';
+         return;
+      }
+
       final extending = new ClientExtendedExtendedRoot();
 
       extending.addValue();