73cda83548
This commit adds lots of plumbing to get the type section from the module linking proposal plumbed all the way through to the `wasmtime` crate and the `wasmtime-c-api` crate. This isn't all that useful right now because Wasmtime doesn't support imported/exported modules/instances, but this is all necessary groundwork to getting that exported at some point. I've added some light tests but I suspect the bulk of the testing will come in a future commit. One major change in this commit is that `SignatureIndex` no longer follows type type index space in a wasm module. Instead a new `TypeIndex` type is used to track that. Function signatures, still indexed by `SignatureIndex`, are then packed together tightly.
This is the wasmtime-environ crate, which contains the implementations
of the ModuleEnvironment and FuncEnvironment traits from
cranelift-wasm. They effectively
implement an ABI for basic wasm compilation that defines how linear memories
are allocated, how indirect calls work, and other details. They can be used
for JITing, native object files, or other purposes.