32bit Architecture availability

The opam file for this library says:
```
available: arch != "arm32" & arch != "x86_32"
```

Inside the library itself, I don't immediately see a dependency on the number of bits in a word. Is this a fundamental constraint or can it be removed without too much work?

Start with the availability constraint in the opam file and inspect the library sources for assumptions about word size or the excluded architectures. Determine whether the constraint can be removed safely; done means either removing it with validation on 32-bit architectures or documenting the fundamental limitation.

Written by the indexing model from the issue text.