functional: new zip and zip_with replace list transpose and zip_with.

* specs/functional_spec.yaml (zip, zip_with): Specify behaviour
of new general zip and zip_with apis.
* lib/std/functional.lua (zip, zip_with): New functions.
* lib/std/list.lua (transpose, zip_with): Deprecate.
* specs/list_spec.yaml (transpose, zip_with): Specify deprecation
warning behaviours.
* NEWS: Update.

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