Add 3 new entries:
o __FreeBSD_version bumped to 502122
o Alpha console initialization requires the same sio(4) hints as on

other platforms. Options NO_SIO and DEV_SC removed.

o KDB framework: Added KDB and GDB; Renamed WITNESS_DDB, DDB_TRACE

DDB_UNATTENDED. Removed GDB_REMOTE_CHAT and DDB_NOKLDSYM.