patch 8.1.0366: pieces of the xdiff code are not used

Problem:    Pieces of the xdiff code are not used.
Solution:   Add "#if 0" to omit unused code.
diff --git a/src/version.c b/src/version.c
index c9a95ed..32f0d1d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    366,
+/**/
     365,
 /**/
     364,