'n_iterations' was no longer used after commit 45c2d96. Before then, …

…we just checked it with an assert() to verify that we weren't going into some sort of endless loop. The assert() seems like a reasonable idea, and I could imagine needing the number of iterations at some point, and... without the assert, gcc can complain of an unused variable. So, reverting.

elem_out.cpp

@@ -4170,6 +4170,7 @@ static void improve_mpc_colors( const int n_obs, const OBSERVE FAR *obs,
          assert( color >=0 && color < max_n_colors);
          }
       n_iterations++;
+      assert( n_iterations < 10);
       }
 }