patch 7.4.1844
Problem:    Using old function name in comment.  More functions should start
            with test_.
Solution:   Rename function in comment. (Higashi Higashi) Rename
            disable_char_avail_for_testing() to test_disable_char_avail().
            And alloc_fail() to test_alloc_fail().
diff --git a/src/getchar.c b/src/getchar.c
index c771117..81cb837 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1880,7 +1880,7 @@
     int	    retval;
 
 #ifdef FEAT_EVAL
-    /* When disable_char_avail_for_testing(1) was called pretend there is no
+    /* When test_disable_char_avail(1) was called pretend there is no
      * typeahead. */
     if (disable_char_avail_for_testing)
 	return FALSE;