Validate save

Trying to run fuzzer on restore function caused crashes. 164 unique, millions repeated. This is an attempt to validate save file to prevent all the out of bounds errors. Save files may still be unreachable by gameplay or malformed in any other way, but they are beyond the purpose of this MR

Note: There's a lack of validating the bounds of game.prop[OBJECT]. Because it needs to be object-defined. Some got 2 states, some 3, bird - 6. Will investigate and improve MR at later date.

Cuts crashes down to 77.

This patch cuts crashes down to 50.

weird_loop.adv

Found a save that causes weird loop of
'The stream flows out through a pair of 1 foot diameter sewer pipes.
It would be advisable to use the exit.

A mysterious recorded voice groans into life and announces:
"This exit is closed. Please leave via main office."'

unmarked as a Work In Progress

changed the description

Only one crash remains. Save file attached:

crasher.adv

There is also a crash on seriously negative values of numdie that I can't prevent due to negative numdie being used in tests

Ok, this prevents crashes due to bad savefile. May need changes to improve API.

I want to break save format to pull PRNG constants out of save file. Also would allow to remake everything into constant width integers.

But I feel that save format breakage isn't my decision to make.

merged