array: a new Object based array for queue and stack-like ops.

* specs/array_spec.yaml: New file. Specify base behaviours for a
new array object.
* specs/specs.mk (specl_SPECS): Add specs/array_spec.yaml.
* lib/std/array.lua: New file. Implement specified behaviours.
* build-aux/config.ld.in (files): Add lib/std/array.lua.
* local.mk (dist_classes_DATA): Add doc/std.array.html.
(dist_luastd_DATA): Add lib/std/array.lua.
* NEWS: Update.

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