patch 9.0.0636: underline color may not work in some terminals

Problem:    Underline color does not work in terminals that don't send a
            termresponse.
Solution:   Do output t_8u if it was set explicitly. (closes #11253)
diff --git a/src/version.c b/src/version.c
index 571eef2..2534e06 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    636,
+/**/
     635,
 /**/
     634,