>Revert "QR_INUSE flag is no longer relevant. Removed it."
Geez. That was quite the fail.
QR_INUSE was a holdover from the days between 1987 and 1998, when the rooms
table was a flat file containing a fixed number of records. QR_INUSE meant
that a particular slot in the file held an active record; its absence meant
that a new room could be stored there.
That isn't really needed anymore because when we remove a record (from any
table) it is simply deleted from the database, so there's no longer any reason
to have a flag that says "yes, this is a real record and not empty space."
I thought I removed it properly, but a little while later, half of my test
system vanished. I still don't know exactly why, but it's definitely something
in that commit. So it's back for now.
