table: add string support to totable function.

* ext/std/table.lua (totable): When passed a string, return a
table of each character in the string.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
Revert "maint: move lua extension sources to $top_srcdir/ext."

This reverts commit 4d51ca63a1eedd3759201db8b3df850a658856e6.

I have no idea why I thought moving Lua libraries from the lib
tree to the Lua C extensions ext tree seemed like a good idea.
Undo the damage.
* ext/: Rename back to lib/.
* local.mk (std_path, dist_lua_DATA, dist_luastd_DATA)
(mkrockspecs_args, EXTRA_DIST, dist_files_DATA)
(dist_modules_DATA): Adjust.
* doc/config.ld (file): Adjust.
* .gitignore: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
container: new module for objects that use [] to access contents.

* specs/container_spec.yaml: Specify behaviour of Container
objects.
* specs/specs.mk (specl_SPECS): Add specs/container_spec.yaml.
* specs/object_spec.yaml: Remove duplicate tests.
* doc/config.ld (file), local.mk (dist_luastd_DATA): Add
lib/std/container.lua.
* lib/std/container.lua: New file. Implement Container objects.
They have no methods, so that __index can be used for accessing
contents instead.
* lib/std/object.lua: Vastly improved doc-comments.
Simplify drastically in light of Container implementation.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
list: remove trailing whitespace.

* lib/std/list.lua: Remove trailing whitespace.

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