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