Change the USB event mechanism to include more information about devices
and drivers. Partly from FreeBSD.

Add an argument to usbd_open_pipe_intr() to specify the polling interval
for an interrupt pipe in case we don't what what the descriptor suggests.

Add some more debug printing.

Cosmetic changes and some small improvements. From FreeBSD and Nick Hibma.

A number of stylistic changes to increase readability (many suggested
by Nick Hibma):
use NULL not 0
declare all local definitions static
rename s/usbd_request/usbd_xfer/ s/reqh/xfer/
rename s/r/

A number of stylistic changes to increase readability (many suggested
by Nick Hibma):
use NULL not 0
declare all local definitions static
rename s/usbd_request/usbd_xfer/ s/reqh/xfer/
rename s/r/err/
use implicit test for no err
KNF

show more ...

Merge in a large batch of changes from Nick Hibma <hibma@skylink.it> so
the USB stack compiles on FreeBSD again.

Fix some bugs in USB controller detach code.

Remove an obsolete comment.

Add preliminary (untested) code for detaching the USB host controller
(needed for CardBus based controllers).

Rearrange the code a little so we can decide if we are in process
or interrupt context in a reliable way. Mainly used for DIAGNOSTIC.

Add a flag in the request to determine if the data copying is done by the
driver or the usbdi layer.

Change the way the `struct device' base part of all driver softc are
declared and accessed to make it more portable. Idea from Nick Hibma, FreeBSD.
No functional changes.

Avoid null reference, from Nick Hibma, FreeBSD.

Change some 'struct device' to 'bdevice'. From FreeBSD.

Make sure to mark the device as dying already in the (de)activate routine.
This avoids access to it before the detach routine has blown it away.

Move more of the transfer completion processing to HC independent code.
Fix some problems with transfer abort & timeout.

Add a utility function, usbd_errstr(), to print error strings. From FreeBSD.

Make some small changes to make it compile on OpenBSD.

Some changes from FreeBSD (no functional differences).

Totally redo the way device detach is done. It now uses a kernel event
thread and the config detach method.
Squish a number of space leaks on detach.

Check that the hub ports actually power up.

Some minor updates from FreeBSD.

Update/add URLs to relevant USB specs.

Various little fixes from the FreeBSD version.

Split usbd_delay_ms() into two functions, one can be used in
device drivers.