patch 8.1.0066: nasty autocommand causes using freed memory

Problem:    Nasty autocommand causes using freed memory. (Dominique Pelle)
Solution:   Do not force executing autocommands if the value of 'syntax' or
            'filetype' did not change.
diff --git a/src/version.c b/src/version.c
index 192b6cd..d3c7316 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    66,
+/**/
     65,
 /**/
     64,