specs: set initial describe headers consistently.

* specs/curses_spec.yaml, specs/posix_compat_spec.yaml,
specs/posix_ctype_spec.yaml, specs/posix_deprecated_spec.yaml,
specs/posix_fcntl_spec.yaml, specs/posix_fnmatch_spec.yaml,
specs/posix_grp_spec.yaml, specs/posix_pwd_spec.yaml,
specs/posix_sys_msg_spec.yaml,
specs/posix_sys_resource_spec.yaml,
specs/posix_sys_stat_spec.yaml,
specs/posix_sys_statvfs_spec.yaml,
specs/posix_sys_time_spec.yaml, specs/posix_sys_times_spec.yaml,
specs/posix_sys_utsname_spec.yaml, specs/posix_time_spec.yaml,
specs/posix_unistd_spec.yaml: Use dot delimmited module names
consistently in initial describe heading.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
posix: move openpty utility into posix and add argchecks.

* lib/posix/util.lua (openpty): Move from here...
* lib/posix.lua (openpty): ...to here.  Add argcheck wrapper.
* lib/posix/util.lua: Reexport openpty for backwards compatibility.
* specs/posix_spec.yaml (openpty): Add specs for argchecks.
* build-aux/config.ld.in (file): Remove lib/posix/util.lua.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>