patch 7.4.1857
Problem:    When a channel appends to a buffer that is 'nomodifiable' there is
            an error but appending is done anyway.
Solution:   Add the 'modifiable' option.  Refuse to write to a 'nomodifiable'
            when the value is 1.
diff --git a/src/version.c b/src/version.c
index e47ab53..c3afbad 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1857,
+/**/
     1856,
 /**/
     1855,