patch 8.1.1194: typos and small problems in source files

Problem:    Typos and small problems in source files.
Solution:   Small fixes.
diff --git a/src/channel.c b/src/channel.c
index dd47c5b..ca83102 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -1906,7 +1906,7 @@
 
     if (prepend)
     {
-	/* preend node to the head of the queue */
+	// prepend node to the head of the queue
 	node->rq_next = head->rq_next;
 	node->rq_prev = NULL;
 	if (head->rq_next == NULL)
@@ -1917,7 +1917,7 @@
     }
     else
     {
-	/* append node to the tail of the queue */
+	// append node to the tail of the queue
 	node->rq_next = NULL;
 	node->rq_prev = head->rq_prev;
 	if (head->rq_prev == NULL)