patch 8.2.4699: hard to reproduce hang when reading from a channel

Problem:    Hard to reproduce hang when reading from a channel.
Solution:   Check for readahead before starting to wait. (closes #10093,
            closes #7781, closes #6364)
diff --git a/src/version.c b/src/version.c
index 23b2a1e..120633f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4699,
+/**/
     4698,
 /**/
     4697,