Add unicode string test case.
Add unicode string test case.

Test that a multibyte unicode character is preserved when going to/from
json and that its \u unicode escape is interpreted correctly.

Signed-off-by: Troy Crosley <3e44ae544d86cf41d60b763030d861d95a7482f7@ainfosec.com>

QtMark/qmjson,QtMark/qmjson,QtMark/qmjson