patch 8.0.0851: 'smartindent' is used even when 'indentexpr' is set

Problem:    'smartindent' is used even when 'indentexpr' is set.
Solution:   Ignore 'smartindent' when 'indentexpr' is set. (Hirohito Higashi)
diff --git a/src/version.c b/src/version.c
index c5c39fe..a5a3d68 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    851,
+/**/
     850,
 /**/
     849,