kes Write new subroutine is_volume_purged() that explicitly checks

kes  Write new subroutine is_volume_purged() that explicitly checks
     if the Volume is purged, and if so marks it as such. This should
     resolve problems reported about needing to mount twice to recycle
     volumes.
kes  Rewrite pruning algorithm to do more work in the SQL engine, and
     to pass a list of JobIds to be deleted to SQL.  Also, minimize the
     amount of duplicated code.
kes  Do volume pruning only for the Media Type desired (reduces pruning time
     if multiple Media Types are in the same pool).
kes  Implement more detailed info in the Job report for the Bacula version
     and architecture.
kes  Switch from POOLMEM to POOL_MEM (a real class) in ua_prune.c and
     ua_purge.c.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@4408 91ce42f0-d328-0410-95d8-f526ca767f89