Python bindings: core.Stream missing close method?

Hi,

It looks like the core.Stream class does not close the underlying streams. It
does save reference to a svn_stream_t wrapper in self._stream, but does not
call svn_stream_close() on its own deletion, nor does the auto-generated
svn_stream_t class do so.

Obviously, it can be closed by calling core.svn_stream_close(s._stream) - but
this accesses private fields not intended to be used as external interfaces.

Am I right that it leaks open streams? If I am - perhaps, fix as attached - to
implement the file-object-like behavior for core.Stream?

Regards,
Alexey.