patch 8.0.0860: side effects when channel appends to a buffer

Problem:    There may be side effects when a channel appends to a buffer that
            is not the current buffer.
Solution:   Properly switch to another buffer before appending. (Yasuhiro
            Matsumoto, closes #1926, closes #1937)

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    860,
 /**/
     859,
 /**/