Mark ``Py_UNICODE_COPY``, ``Py_UNICODE_FILL``, ``PyUnicode_WSTR_LENGTH``,
``PyUnicode_FromUnicode``, ``PyUnicode_AsUnicode``,
and ``PyUnicode_AsUnicodeAndSize`` as deprecated in C. Remove ``Py_UNICODE_MATCH``
which was deprecated and broken since Python 3.3.
