vtracks with virtual track numbers can't be ripped with external rippers

[cassella]

The default ripcmdline is

-d %c %t:[.%s]-%t:[.%e] %w

As it stands, %t gets replaced with the vtracknum, so the ripper is asked to rip something nonsensical.

Unfortunately, when vtracks are involved, the two %t may need to get different values.

The grip-internal libcdda_paranoia ripper works.