Prevent 100% CPU usage when there's a unit in focus

The time until next frame was repeatedly divided by 1000, resulting in 0 wait
at the end.

See #782.
See #789.

client/client_main.cpp

@@ -1095,14 +1095,12 @@ double real_timer_callback()
 
   {
     double blink_time = blink_turn_done_button();
-
-    time_until_next_call = MIN(time_until_next_call, blink_time) / 1000;
+    time_until_next_call = std::min(time_until_next_call, blink_time / 1000);
   }
 
   if (get_num_units_in_focus() > 0) {
     double blink_time = blink_active_unit();
-
-    time_until_next_call = MIN(time_until_next_call, blink_time) / 1000;
+    time_until_next_call = std::min(time_until_next_call, blink_time / 1000);
   }
 
   /* It is possible to have current_turn_timeout() > 0 but !turndone_timer,
@@ -1113,7 +1111,7 @@ double real_timer_callback()
       update_timeout_label();
     }
 
-    time_until_next_call = MIN(time_until_next_call, 1.0);
+    time_until_next_call = std::min(time_until_next_call, 1.0);
   }
   if (waiting_turn_change) {
     double seconds =
@@ -1136,6 +1134,7 @@ double real_timer_callback()
     }
   }
 
+  qCritical() << time_until_next_call;
   return std::max(time_until_next_call, 0.0);
 }