warn the user it will take a while

tests/rm/hash

@@ -18,6 +18,7 @@ mkdir $tmp || framework_failure=1
 cd $tmp
 
 # Create a hierarchy with 3*26 leaf directories, each at depth 153.
+echo "$0: creating 78 trees, each of depth 153; this will take a while..." >&2
 y=`yes |tr '\012' / |head -c 300`
 for i in 1 2 3; do
   for j in a b c d e f g h i j k l m n o p q r s t u v w x y z; do