patch 8.1.0215: no error if configure --with-x cannot configure X

Problem:    No error if configure --with-x cannot configure X.
Solution:   Check that when --with-x is used X can be configured.
diff --git a/src/version.c b/src/version.c
index 087bc63..172748b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -799,6 +799,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    215,
+/**/
     214,
 /**/
     213,