New versioning scheme

Note that beginning with the next release, QMC2 (as well as QMC2 Arcade and Qt CHDMAN GUI) will use the same version as the respective MAME release.

This should avoid confusion about the MAME version it’s compatible to / synced with in the future. I’ve been asked several times about it, and now since the last digit doesn’t match anymore it’s probably more of an issue for users not reading the change-log closely (before it was “MAME version minus 110”, now it’s “MAME version minus 111” and it’s possible I’ll skip other MAME releases in the future as well, so I suppose it makes sense).