Support for multi-value wasm (#399)

* deps: bump wasmparser to 0.39.2

This has a bug fix for multi-value Wasm validation that is required for getting
the spec tests passing.

https://github.com/yurydelendik/wasmparser.rs/pull/135

* Update cranelift to 0.46.1 to get multi-value Wasm support

The `cranelift_wasm` APIs had to change a little bit to maintain state necessary
when translating multi-value Wasm blocks. The `translate_module` function now
returns a `ModuleTranslationState` that is borrowed during each function's
translation.

* Enable multi-value proposal's spec tests

This enables all the Wasm multi-value proposal's spec tests other than the ones
that rely on functions having more return values than registers available on the
target. That is not supported by cranelift yet.

* wasmtime-interface-types: always use multi-value Wasm

And remove the return pointer hacks that work around the lack of multi-value.

misc/wasmtime-rust/macro/src/lib.rs

@@ -59,7 +59,10 @@ fn generate_load(item: &syn::ItemTrait) -> syn::Result<TokenStream> {
             let mut cx = #root::wasmtime_jit::Context::with_isa(
                 isa,
                 #root::wasmtime_jit::CompilationStrategy::Auto
-            );
+            ).with_features(#root::wasmtime_jit::Features {
+                multi_value: true,
+                ..Default::default()
+            });
             let data = #root::wasmtime_interface_types::ModuleData::new(&bytes)?;
             let handle = cx.instantiate_module(None, &bytes)?;