* lib/math.in.h (totalordermagf): New declaration.
* lib/totalordermagf.c: New file, based on lib/totalorderf.c.
* m4/math_h.m4 (gl_MATH_H): Test whether totalordermagf is declared.
(gl_MATH_H_REQUIRE_DEFAULTS): Initialize GNULIB_TOTALORDERMAGF.
(gl_MATH_H_DEFAULTS): Initialize HAVE_TOTALORDERMAGF,
REPLACE_TOTALORDERMAGF.
* modules/math (Makefile.am): Substitute GNULIB_TOTALORDERMAGF,
HAVE_TOTALORDERMAGF, REPLACE_TOTALORDERMAGF.
* modules/totalordermagf: New file, based on modules/totalorderf.
* doc/posix-functions/totalordermagf.texi: Mention the new module.