patch 8.1.1630: various small problems

Problem:    Various small problems.
Solution:   Various small improvements.
diff --git a/src/list.c b/src/list.c
index e7a4f99..e1aa2d1 100644
--- a/src/list.c
+++ b/src/list.c
@@ -130,7 +130,7 @@
 
 
 /*
- * Set a list as the return value
+ * Set a list as the return value.  Increments the reference count.
  */
     void
 rettv_list_set(typval_T *rettv, list_T *l)