vector: remove unneeded module.

On second thoughts, this is not necessary.  Adding methods to core
table would give us the API benefits, and posix.curses.chstr is a
much easier way of handling arrays of attributed strings.
* lib/std/vector.lua: Remove.
* build-aux/config.ld.in (file): Remove lib/std/vector.lua.
* local.mk (dist_luastd_DATA): Likewise.
(dist_classes_DATA): Remove doc/classes/std.vector.html.
* specs/vector_spec.yaml: Remove.
* specs/string_spec.yaml (render): Remove vector examples.
* specs/specs.mk (specl_SPECS): Remove specs/vector_spec.yaml.
* NEWS: Remove vector references.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
io: add dirname function again.

* specs/io_spec.yaml (dirname): Specify behaviour of a new
function to discard the final path separator in a string and all
that follows.
* lib/std/io.lua (M.dirname): Implement it.
* NEWS: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
string: don't return spurious additional values.

* lib/std/base.lua (escape_pattern): Wrap gsub return value in
parens to strip all but the first string return value.
* lib/std/string.lua (caps, chomp, escape_shell, ltrim, rtrim)
(trim): Likewise.

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