[Typed objects] Guard against integer overflow issues

[trev]

Background

The current memory allocation implementation for typed objects doesn't guard against integer overflows. In particular, there can be at most 32768 buffers for each type but we will happily try to allocate more buffers.

What to change

Check where integer overflows can happen in the code and add guards to produce a meaningful error message in that case.

[fhd]

Since the Emscripten based approach is looking rather good, I'm not sure we really want to continue to work on Typed Objects. Makes it a P5.

[trev]

In fact, at that point I am certain that we are dropping typed objects and go with Emscripten instead. The performance issues we had with Emscripten initially are bound to affect us with typed objects as well (important points: static generation of JS bindings, stack-based allocations, likely more). Fixing these issues was already non-trivial with Emscripten, but with our own toolchain it will require far more effort - this isn't going to pay off if we have a reasonable and maintained alternative.