The f64 -> int serialization has broken determinism

[dabreegster]

#686 gave us some great file size savings, but I've hit a few unexpected problems since then: 137e9a0 and 9f4fac5. And now I have a case where running from a simulation savestate crashes with a queue overflow (by Distance(-0.0001)), but it runs fine without the serialization/deserialization round-trip.

I thought the change was safe; the conversion to/from ints should be lossless. But it looks like the f64 trimming must not work the way I expect.

Options:

• Dig into why the f64 trimming isn't actually working
• Revert these commits and go back to f64s
• Change the in-memory representation of the geom types to be integers

[dabreegster]

Closed by 1063