This patch adds the posibility to filter out certain devices from redirecion.
To use this pass the filter property to -device usb-redir.  The filter
property takes a string consisting of filter rules, the format for a rule is:
<class>:<vendor>:<product>:<version>:<allow>

-1 can be used to allow any value for a field.

Muliple rules can be concatonated using | as a separator. Note that if
a device matches none of the passed in rules, redirecting it will not be
allowed!

Example:
-device usb-redir,filter='-1:0x0781:0x5567:-1:0|0x08:-1:-1:-1:1'

This example will deny the Sandisk Cruzer Blade being redirected, as it
has a usb id of 0781:5567, it will allow any other usb mass storage devices,
and it will deny any other devices (the default for devices not matching any
of the rules.

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