Next step in making usb more newbus:

Next step in making usb more newbus:
o reprobe children when a new driver is added to uhub
o fix the usbd_probe_and_attach to set the ivars to a malloc'd area, as well
  as freeing the ivars on child destruction.
o Don't delete children that don't attach. Evidentally, the need to do this
  is a common misconception.
o minor formatting foo that may violate style(9) at the moment, but keeps the
  diffs against my p4 tree smaller.

This does not solve the ugen gobbling things up problem, but the fixes
I have for that expose bugs in other parts of the tree...