This patch addresses some of the minor problems with programming
USB with "usbfs", or coming up with any kind of usb slave/target
device driver API (including eventually USB-OTG).

It does so by creating a new <linux/usb_ch9.h> file that defines
common constants and descriptor structures that are now found in
<linux/usb.h> but which are (a) not exported to userspace, making
programming with "usbfs" awkward, and (b) needlessly mixed up with
the usb master/host-only side APIs, which a slave/target-only side
API will not want to require.  These definitions are just moved out
of <linux/usb.h>, so they can be accessed safely.


If folk agree that this should be done, instead of different headers
and declarations for master/host, slave/target, and dual-mode OTG
(which was the road the Lineo APIs, rejected by Linus, started down),
I think this should be merged (compiles but untested) as a start.

Then configuration, interface, and device descriptors could get split
out too.  That'd involve some code changes, since those descriptor
structures have been augmented (or maybe "sullied"?) with data that's
specific to the Linux host-side driver implementation.  So they're
currently unsuitable to be used by user-space or slave/target drivers.