Request commands are even, responses odd.
Remove unused.
value_string: Use unsigned as index_type.

But logically divide it into lower 16 bits offset, upper
16 bits length. All-zero means whole record.

Why I don't just remove this code is beyond me.
Print message when tests done.
Add Json::as_u.
Add Json::end_array_data().
msgpack: Add format::is_() functions, add parse_array_size.
msgpack: Add parser::skip_primitive and skip_array_size.
Move testrunner into its own header.

Going to use it elsewhere.
Use testrunner in mtclient.
Add wcol1/rcol1 tests to mtclient.
Add StringAccum::set_end