This should cause maps that have the same
seeds to have much more similar results
than before, e.g. sponge deposits will be in
the same places determined by seed and not
random each regeneration of the map.
- Mapgen shared now provides an RNG which
will be deterministic when feasible, for
repeatable mapgen results.
- Make existing rng-using mapgen hooks use
the new deterministic RNG.
- Mapgen shared hooks are also run in
deterministic order too.
- Tidy up mapgen_shared API a little more.
- Categorize types of issues, since I find I pick through the list
not based on absolute priority but based on what kind of things
I feel like working on, e.g. gameplay improvements vs. code
quality.
- Clean out the icebox. Reinstate a few things at bottom of other
lists, clean out the rest.
