cbrtl-ieee: Work around test failure on IRIX 6.5. * m4/cbrtl-ieee.m4: New file. * m4/cbrtl.m4 (gl_FUNC_CBRTL): If gl_FUNC_CBRTL_IEEE is present, test whether cbrtl works with a minus zero argument. Replace it if not. * lib/math.in.h (cbrtl): Override if REPLACE_CBRTL is 1. * m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_CBRTL. * modules/math (Makefile.am): Substitute REPLACE_CBRTL. * modules/cbrtl (configure.ac): Consider REPLACE_CBRTL. (Depends-on): Update conditions. * modules/cbrtl-ieee (Files): Add m4/cbrtl-ieee.m4, m4/minus-zero.m4, m4/signbit.m4. (configure.ac): Invoke gl_FUNC_CBRTL_IEEE. * lib/cbrtl.c (cbrtl) [IRIX]: Avoid an unnecessary addition. * doc/posix-functions/cbrtl.texi: Mention the cbrtl-ieee module.

# cbrtl-ieee.m4 serial 1
dnl Copyright (C) 2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

dnl This macro is in a separate file (not in cbrtl.m4 and not inlined in the
dnl module description), so that gl_FUNC_CBRTL can test whether 'aclocal' has
dnl found uses of this macro.

AC_DEFUN([gl_FUNC_CBRTL_IEEE],
[
  m4_divert_text([INIT_PREPARE], [gl_cbrtl_required=ieee])
  AC_REQUIRE([gl_FUNC_CBRTL])
])