O_BINARY for win32 GIOChannel

[Ron Steinke <rsteinke w-link net>]

	There's one alternative for handling this we haven't
considered yet: always set O_BINARY, and then fake it
in g_io_channel_write_chars() before doing the conversion,
i.e. if channel->encoding != NULL add a \r before every \n
just before we pass it through iconv. This would be a little
messy to implement, but provides the most straightforward
API.

Ron Steinke