dae04be948
As suggested [here](https://github.com/Amanieu/hashmap_core/pull/10#issuecomment-455866083). This also allows us to re-enable the basic compile fuzz target.
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.