(byte-recompile-directory): Doc fix.

lisp/emacs-lisp/bytecomp.el

@@ -1055,11 +1055,14 @@ otherwise pop it")
 (defun byte-recompile-directory (directory &optional arg)
   "Recompile every `.el' file in DIRECTORY that needs recompilation.
 This is if a `.elc' file exists but is older than the `.el' file.
+Files in subdirectories of DIRECTORY are processed also.
 
 If the `.elc' file does not exist, normally the `.el' file is *not* compiled.
 But a prefix argument (optional second arg) means ask user,
 for each such `.el' file, whether to compile it.  Prefix argument 0 means
-don't ask and compile the file anyway."
+don't ask and compile the file anyway.
+
+A nonzero prefix argument also means ask about each subdirectory."
   (interactive "DByte recompile directory: \nP")
   (if arg
       (setq arg (prefix-numeric-value arg)))