…rrays

The :mod:`asyncio` code is writing binary data to a :class:`socket.socket`, and
advancing through the buffer after a partial write by doing
``memoryview(data)[n:]``, where ``n`` is the number of bytes written.

This assumes the :class:`memoryview` is a one dimensional buffer of bytes,
which is not the case e.g. for a :class:`memoryview` of an :class:`array.array`
of non-bytes, or an ``ndarray`` with more than one dimension. Partial writes of
such :class:`memoryview`s will corrupt the stream, repeating or omitting some
data.

When creating a :class:`memoryview` from a :class:`memoryview`, first convert
it to a one-dimensional array of bytes before taking the remaining slice, thus
avoiding these issues.

Add an assertion that the remaining data is bytes, to guard against possible
regressions if additional types of data are allowed in the future.

Hopefully this will fix the windows compile failures...