* lib/math.in.h (logbl): New declaration.
* lib/logbl.c: New file.
* m4/logbl.m4: New file.
* m4/math_h.m4 (gl_MATH_H): Test whether logbl is declared.
(gl_MATH_H_DEFAULTS): Initialize GNULIB_LOGBL, HAVE_LOGBL,
REPLACE_LOGBL.
* modules/math (Makefile.am): Substitute GNULIB_LOGBL, HAVE_LOGBL,
REPLACE_LOGBL.
* modules/logbl: New file.
* tests/test-math-c++.cc: Check the declaration of logbl.
* doc/posix-functions/logbl.texi: Mention the new module.
* m4/printf.m4 (gl_PRINTF_INFINITE_LONG_DOUBLE): Don't guess yes on
NetBSD; the test fails on NetBSD 5.0.
* doc/{glibc,posix,pastposix}-{headers,functions}/*.texi: Update info
about NetBSD.