This stream will forward all stream operations to the selected stream,
but will forward all connection related operations to the given
ConnectionStream. This allows wrapping embedded streams, such as
SSL streams in a ConnectionStream.
Returns the maximum number of bytes that are known to remain in this stream until the
end is reached. After leastSize() bytes have been read, the stream will either have
reached EOS and empty() returns true, or leastSize() returns again a number > 0.