update: Use a scratch sctstr for unit repair simulation

update: Use a scratch sctstr for unit repair simulation

If player->simulation, shiprepair(), planerepair(), landrepair() must
use the bp map, and must not change game state.

Copy the sector to a scratch buffer, update it from the bp map, work
on the sector normally, then write back to the bp map.  This is
simpler and safer.

Since get_materials() loses its connection to the bp map, move its
declaration out of budg.h.

While there, drop an ancient debugging logerror() from landrepair().

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