Add some new mouse ranges called "control0" to "control9", will be used

for controls on floating panes, from Dane Jensen, with some bits from
Michael Grant.

format.c

@@ -1307,6 +1307,8 @@ format_cb_mouse_status_range(struct format_tree *ft)
 		return (xstrdup("session"));
 	case STYLE_RANGE_USER:
 		return (xstrdup(sr->string));
+	case STYLE_RANGE_CONTROL:
+		return (xstrdup("control"));
 	}
 	return (NULL);
 }