object: enhance prototype to recognize file objects.

* specs/object_spec.yaml (prototype): Specify results of passing
file handles and Lua primitives to prototype.
* lib/std/object.lua (prototype): Improve LDocs.
* lib/std/base.lua (prototype): Enhance implementation to meet
new specifications.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
io: complete specs and improve LDocs.

* lib/std/io.lua (catdir, catfile, die, monkey_patch)
(process_files, readlines, shell, slurp, splitdir, warn)
(writelines): Improve LDocs with usage examples and cross-
references.
* specs/io_spec.yaml (catdir, catfile, die, monkey_patch)
(process_files, readlines, shell, slurp, splitdir, warn)
(writelines): Add missing specificatons.
* specs/spec_helper.yaml (concat_file_content): New function to
support new specifications.
(luaproc): Support subprocess arguments and standard input.

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