* Forget all cached info when opening a new disc.
* If the disc is removed, flush the buffer queue rather than stalling it.
* Set the default label after getting the disc size, and fill in the info
for RAW_PART also.
* Change another use of the unit number to a softc pointer.
* Use a dkdevice to hold the label and open partition masks.
* Force the partition offset to 0 for RAW_PART, regardless of the label.
* Nuke MCDPHYS() and MCDREADRAW; they had a silly bug that caused the code
to not work, and they aren't useful anyway.
Some other minor cleanup.
9769a6a6f7