Windows: move the right control for align_next_to.

We had carefully calculated, for each control in an aligned group, how
much _that control_ should move downwards by. But then, because I
carelessly referred to the wrong variable name, we actually moved the
wrong one - not the control we'd just calculated the offset for, but
always the _last_ one in the group, which was the one the top-level
alignment code was processing at the point we began this loop.

As a result, the dropdown list in the front-page protocol selector was
hilariously misaligned. Now it's back where it should be.

windows/controls.c

@@ -1758,7 +1758,7 @@ void winctrl_layout(struct dlgparam *dp, struct winctrls *wc,
                         continue;
 
                     LONG dy = (mid2 - (rect.top + rect.bottom)) / 2;
-                    move_windows(pos.hwnd, c->base_id, c->num_ids, dy);
+                    move_windows(pos.hwnd, thisc->base_id, thisc->num_ids, dy);
                 }
             }
         } else {