#67 Multi-artist handling (updates #527978)

[Phil Stracchino]

This patch is an update of, and extension, to patch
#527978. It is updated to work with Grip-2.99.0, and
extended to also provide alternate filename handling
for .m3u files and ripfiles on multi-artist CDs. The
ripfile handling is pretty much gravy, as it's
transient anyway, but there may well be times when you
want it, for instance if you're just ripping WAV files
to compile onto an audio CD.

[Phil Stracchino]

Patch for multi-artist handling in Grip-2.99.0