patch 8.1.1633: cannot generate prototypes with X11 but without GUI

Problem:    Cannot generate prototypes with X11 but without GUI.
Solution:   Include X11/Intrinsic.h.
diff --git a/src/version.c b/src/version.c
index 59c3c51..20bff05 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1633,
+/**/
     1632,
 /**/
     1631,