* fhandler.h (fhandler_socket::read): Remove method.

	* fhandler.h (fhandler_socket::read): Remove method.
	(fhandler_socket::write): Ditto.
	(fhandler_socket::readv): New method.
	(fhandler_socket::writev): Ditto.
	(fhandler_socket::recvmsg): Add new optional argument.
	(fhandler_socket::sendmsg): Ditto.
	* fhandler.cc (fhandler_socket::read): Remove method.
	(fhandler_socket::write): Ditto.
	(fhandler_socket::readv): New method.
	(fhandler_socket::writev): Ditto.
	(fhandler_socket::recvmsg): Use win32's scatter/gather IO where
	possible.
	(fhandler_socket::sendmsg): Ditto.
	* net.cc (cygwin_recvmsg): Check the msghdr's iovec fields.
	(cygwin_sendmsg): Ditto.  Add omitted sigframe.