(grow_islands, set_coastal, update_coastal_flag, coast_sea_to_land)
(coast_land_to_sea): Determine sct_coastal flag when the sector type
is set. Old method only updated the sct_coastal flag when doing
cens() or a dump(). Other uses of sct_coastal could get stale values,
including selector coastal. Rework set_coastal() into NEW functions
update_coastal_flag(), coast_sea_to_land(), coast_land_to_sea() and
set_coastal(). Fix a bug where the deity designation would not
properly set the coastal flag. Fix a bug where the one sector lake
would not properly compute coastal flag. Fix a bug that makes
fairland treat the last sector it adds to an island as non-coastal.
(nullify_objects, do_desi): Simpify designate restrictions of options
NO_LCMS, NO_HCMS, NO_OIL.
(show_sect_build): Suppress printing of sectors only deity can
designate. This was broken in rev. 1.15.
thread entrypoints:
(lwpSelect, shutdown_sequence): Parameters didn't match thread entry
point prototype.
(lwpEntryPoint): Arguments didn't match thread entry point prototype.
Change linkage of functions without prototype declaration to static
where possible.
Remove some superflous declarations, replace others by suitable
includes.