Change nation status from bits to a simple enum:

Change nation status from bits to a simple enum:
(nat_status, STAT_UNUSED, STAT_VIS, STAT_ACTIVE): New.
(STAT_NEW, STAT_SANCT, STAT_GOD): Change into nat_status members.
(STAT_INUSE, STAT_NORM): Remove.
(natstr): Use new nat_status for nat_stat.
    New value       Old value
    STAT_UNUSED     0
    STAT_NEW        STAT_INUSE | STAT_NEW
    STAT_VIS        STAT_INUSE
    STAT_SANCT      STAT_INUSE | STAT_SANCT
    STAT_ACTIVE     STAT_INUSE | STAT_NORM
    STAT_GOD        STAT_INUSE | STAT_NORM | STAT_GOD
Users changed.