kes Make find with no args in tree restore return error rather than

kes  Make find with no args in tree restore return error rather than
     stopping the selection. Fixes bug #665
kes  Rework DVD writing to ensure that the last part is written
     on open_next_part when dealing with a spool file.
kes  Correct the lseek_dev() routine to handle end point correctly
     (bug introduced by me).
kes  Allow part number to exceed num_dvd_parts in lseek_dev().