* lib/math.in.h (log1pf): New declaration.
* lib/log1pf.c: New file.
* m4/log1pf.m4: New file.
* m4/math_h.m4 (gl_MATH_H): Test whether log1pf is declared.
(gl_MATH_H_DEFAULTS): Initialize GNULIB_LOG1PF, HAVE_LOG1PF,
REPLACE_LOG1PF.
* modules/math (Makefile.am): Substitute GNULIB_LOG1PF, HAVE_LOG1PF,
REPLACE_LOG1PF.
* modules/log1pf: New file.
* tests/test-math-c++.cc: Check the declaration of log1pf.
* doc/posix-functions/log1pf.texi: Mention the new module.