update: Reorder feeding, tax & plague for consistency

update: Reorder feeding, tax & plague for consistency

People in sectors get plagued, then taxed or paid, then fed.  People
on ships and land units get paid, then fed, then plagued.  Sectors
were messed up when Empire 3 made the update code work for budget.

Change sectors back to how they worked before Empire 3: move do_feed()
from produce_sect() to prepare_sects(), and delay do_plague() until
after do_feed().  People in sectors now get taxed, paid and fed even
when they die of the plague, just like they do on ships and land
units.

Because do_plague() now runs after populace(), the latter's handling
of people dying off doesn't cover plague anymore.  Delay it to the
very end of prepare_sects().

Additionally, move feeding and plaguing from upd_ship(), upd_land() to
prep_ship(), prep_land(), for consistency with sectors.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>