Merge from NetBSD.

o usb_subr.c, add delta 1.119:

Move usb_get_string() and make it public.

o usbdi.c, bring on par with 1.106, this includes:

• Make an iterator abstraction for looping through all descriptors.
• Whine about not being able to figure out default language if we are debugging.
• Move usb_get_string() and make it public.

o usbdi.h, bring on par with 1.64, this includes:

• Make an iterator abstraction for looping through all descriptors.
• Move usb_get_string() and make it public.

o usbdi_util.c, bring on par with 1.42, this includes:

• Add usbd_get_protocol().
• Use NULL instead of 0.
• Fix (mostly harmless) typo.
• Move utility routine from uirda.c to usbdi_util.c.

o usbdi_util.h, bring on par with 1.31, this includes:

• Add usbd_get_protocol().
• Move utility routine from uirda.c to usbdi_util.c.

MFC after: 3 days