printf extension doc bug

[Joseph S. Myers]

The documentation for glibc's feature for customising printf formats is
self-contradictory: it gives an example of %z, but says that lengths
(which now include z) cannot be used as conversions.  This patch changes
the example and adds a warning about using lowercase letters.

--- stdio.texi.orig	Fri Apr 21 22:11:30 2000
+++ stdio.texi	Tue Oct 10 20:59:43 2000
@@ -2098,11 +2098,13 @@
 @comment GNU
 @deftypefun int register_printf_function (int @var{spec}, printf_function @var{handler-function}, printf_arginfo_function @var{arginfo-function})
 This function defines the conversion specifier character @var{spec}.
-Thus, if @var{spec} is @code{'z'}, it defines the conversion @samp{%z}.
+Thus, if @var{spec} is @code{'Y'}, it defines the conversion @samp{%Y}.
 You can redefine the built-in conversions like @samp{%s}, but flag
 characters like @samp{#} and type modifiers like @samp{l} can never be
 used as conversions; calling @code{register_printf_function} for those
-characters has no effect.
+characters has no effect.  It is advisable not to use lowercase letters,
+since the ISO C standard warns that additional lowercase letters may be
+standardized in future editions of the standard.
 
 The @var{handler-function} is the function called by @code{printf} and
 friends when this conversion appears in a template string.

-- 
Joseph S. Myers
jsm28@cam.ac.uk