(NSC_NATID): New.

(NSC_NATID): New.
(sect_ca, NSC_GENITEM, nuke_ca, treaty_ca, loan_ca, news_ca, lost_ca,
commodity_ca, trade_ca, nat_ca): Use it.  Fixes sector selector
che_target.

(NSC_IELT, NSC_GENITEM, ship_ca, plane_ca, nuke_ca, treaty_ca,
news_ca, lost_ca, commodity_ca, trade_ca, nat_ca): Fix initializers
for ca_type.  Harmless signed/unsigned mismatches, except for plane
selectors att, def, nuke selector types, treaty selector exp, news
selector time, commodity selectors type, xbuy, ybuy.

(commodity_ca): Remove NSC_DEITY from selector price.