dnl @synopsis RT_BOOL_ARG_ENABLE([FLAG],[DEFAULT],[HELP STRING])
dnl
dnl This macro declares a configure option with 'AC_ARG_ENABLE'.
dnl It is a boolean argument (yes or no values only), and 
dnl the corresponding shell variable 'enable_arg' is guaranteed to 
dnl be one or the other.
dnl A message is also printed.
dnl
dnl Arguments
dnl $1 = flag name e.g. [debug]
dnl $2 = default value, shall be m4 constant, either [yes] or [no]
dnl $3 = help string (default value is appended) e.g. [compile debugging code]
dnl
dnl @version $Id: rt_bool_arg_enable.m4,v 1.2 2006/02/18 14:35:09 r3mi Exp $
dnl @author Rémi Turboult <r3mi@users.sourceforge.net>
dnl @license GPLWithACException
dnl
dnl This file is free software, distributed under the terms of the GNU
dnl General Public License.  As a special exception to the GNU General
dnl Public License, this file may be distributed as part of a program
dnl that contains a configuration script generated by Autoconf, under
dnl the same distribution terms as the rest of that program.
dnl
AC_DEFUN([RT_BOOL_ARG_ENABLE],[
	dnl
	m4_pushdef([Name],AS_TR_SH($1))dnl
	m4_pushdef([NAME],AS_TR_CPP($1))dnl
	dnl
	AC_MSG_CHECKING([for --enable-]Name)
	dnl
	dnl use some m4 sugar to have only one 'AC_ARG_ENABLE' declaration,
	dnl else "configure --help" is confused
	dnl
	AC_ARG_ENABLE(Name,
		      [m4_case([$2],
		      	[yes],AS_HELP_STRING([--disable-]Name,
			     	         [disable $3 @<:@default=enabled@:>@]),
			[no],AS_HELP_STRING([--enable-]Name,
			     	         [enable $3 @<:@default=disabled@:>@]),
			[m4_fatal([incorrect boolean argument '$2'])]
		               )])
	test "x$enable_[$1]" != [x]m4_if([$2],[yes],[no],[yes]) dnl
		&& enable_[]Name=[$2]
	AC_MSG_RESULT($enable_[]Name)
	AM_CONDITIONAL([ENABLE_]NAME, test x"$enable_[]Name" = xyes)
	dnl
	m4_popdef([NAME])dnl
	m4_popdef([Name])dnl
	dnl
])dnl