patch 7.4.1666

Problem:    When reading JSON from a channel all readahead is used.
Solution:   Use the fill function to reduce overhead.

src/version.c

@@ -748,6 +748,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1666,
 /**/
     1665,
 /**/