patch 8.2.0856: CTRL-S stops output

Problem:    CTRL-S stops output.
Solution:   Invert the IXON flag. (closes #6166)
diff --git a/src/version.c b/src/version.c
index b3aa840..c472819 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    856,
+/**/
     855,
 /**/
     854,