list: base.export module functions for improved argchecks.

* lib/std/list.lua (_functions): Rename from this...
(M): ...to this.  Add a module name entry for export.
* specs/list_spec.yaml (exported_apis): Adjust accordingly.
(append, compare, concat, filter, flatten, map, project, rep)
(sub, tail, transpose, zip_with): Modernize badarg error
specifications.  Specify "too many arguments" error behaviours.
* lib/std/list.lua (cons): Store in M; adjust getcompat/setcompat
id.
(map_with, project, transpose, zip_with): Use export for improved
argchecks.
(append, compare, concat, depair, enpair, filter, flatten, map)
(rep, shape, sub, tail): Likewise.  Remove manual argcheck calls.

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