USB: add usb network redirection support

USB: add usb network redirection support

This patch adds support for a usb-redir device, which takes a chardev
as a communication channel to an actual usbdevice using the usbredir protocol.

Compiling the usb-redir device requires usbredir-0.3 to be installed for
the usbredir protocol parser, usbredir-0.3 also contains a server for
redirecting usb traffic from an actual usb device. You can get the 0.3
release of usbredir here:
http://people.fedoraproject.org/~jwrdegoede/usbredir-0.3.tar.bz2
(getting a more formal site for it is a WIP)

Example usage:
1) Start usbredirserver for a usb device:
sudo usbredirserver 045e:0772
2) Start qemu with usb2 support + a chardev talking to usbredirserver +
   a usb-redir device using this chardev:
qemu ... \
  -readconfig docs/ich9-ehci-uhci.cfg \
  -chardev socket,id=usbredirchardev,host=localhost,port=4000 \
  -device usb-redir,chardev=usbredirchardev,id=usbredirdev

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>