* modules/getloadavg (Files): Add m4/getloadavg.m4.

* modules/getloadavg (Files): Add m4/getloadavg.m4.
(configure.ac): AC_FUNC_GETLOADAVG -> gl_GETLOADAVG, as
the former is now obsolescent.
* lib/getloadavg.c [defined gl_GETLOADAVG]: Don't include config.h
or stdbool.h, because they might not exist while configuring.
* m4/fnmatch.m4: Add comment that Autoconf AC_FUNC_FNMATCH is
obsolescent, and programs should use gnulib instead.
* m4/getloadavg.m4: New file, with contents taken from Autoconf
but with prefixes changed.