patch 8.0.1081: memory leak for the channel write queue

Problem:    Memory leak for the channel write queue.
Solution:   Free the write queue when clearing a channel.
diff --git a/src/version.c b/src/version.c
index 989fe04..0018bce 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1081,
+/**/
     1080,
 /**/
     1079,