remainderl-ieee: Work around test failure on OSF/1.

remainderl-ieee: Work around test failure on OSF/1.

* m4/remainderl-ieee.m4: New file.
* m4/remainderl.m4 (gl_FUNC_REMAINDERL): If gl_FUNC_REMAINDERL_IEEE is
present, test whether remainderl works with a zero second argument.
Replace it if not.
* lib/math.in.h (remainderl): Override if REPLACE_REMAINDERL is 1.
* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_REMAINDERL.
* modules/math (Makefile.am): Substitute REPLACE_REMAINDERL.
* modules/remainderl (configure.ac): Consider REPLACE_REMAINDERL.
(Depends-on): Update conditions.
* modules/remainderl-ieee (Files): Add m4/remainderl-ieee.m4.
(Depends-on): Add remainder-ieee.
(configure.ac): Invoke gl_FUNC_REMAINDERL_IEEE.
* doc/posix-functions/remainderl.texi: Mention the remainderl-ieee
module.