kes Change error message 'illegal' to 'invalid' -- bug #707

kes  Add rather primitive device resource deadlock detection in
     the job queue handler. It detects the same read and write device
     for migration and cancels the job.
kes  Start adding a unique_dbid_hander() routine in migration to avoid
     duplicate mediaids and duplicate jobids.
kes  Add patch from bug #708 to permit relative paths such as ../xxx
     in the restore tree routine.
kes  Add Eric Bollengier's patch to reduce locking time in the SD after
     despooling, and thus many jobs finish faster.
kes  Correct locking order of reservations lock and device mutex in
     reserve.c -- this should correct Arno's deadlock that occurred
     when doing mount/unmount at the same time a job is reserving a
     drive.