[RFC] linux_usbfs: Support kernel capabilities and scatter-gather APIs

[Hans de Goede]

I've been working on some kernel usbfs changes to make live easier for
libusbx, consisting of 2 API additions:
1) An API to query the kernel if it supports things like the
   bulk-continuation flag and other features for which we  currently abuse
   the kernel version to find out if they are supported
2) Support for using scatter-gather lists for large bulk transfers, this
   does not really change the userspace API, but we can take advantage of
   this by simply submitting large transfers in one go, rather then
   splitting it up, with all difficulties that creates for us

The patches in this patch-set add support for these 2 new features. Note this
is strictly a RFC, do not add these patches to the git tree yet, please!

The reason for this is that although the upstream kernel reception of the
patches has been positive. the patches are not in the upstream kernel yet, so
the API may still change!!

Regards,

Hans