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