memory.grow breaks references

[fengb]

When the WASM memory grows, the buffer is invalidated and we have to rebuild the Uint8Arrays. We're working around it by making everything a getter function, but the memory segment is still broken.

Maybe a better solution is to use a proxy object that double checks on access?

Performance is a minor concern here. The actual shipped code will double check only once per render cycle so any direction should be okay.

[fengb]

This is mostly fixed. I'd like to replace the get functions with self memoization.