Update WebAssembly C API submodule to latest commit. (#2579)

* Update WebAssembly C API submodule to latest commit.

This commit updates the WebAssembly C API submodule (for `wasm.h`) to the
latest commit out of master.

This fixes the behavior of `wasm_name_new_from_string` such that it no longer
copies the null character into the name, which caused unexpected failures when
using the Wasmtime linker as imports wouldn't resolve when the null was
present.

Along with this change were breaking changes to `wasm_func_call`, the host
callback signatures, and `wasm_instance_new` to take a vector type instead of a
pointer to an unsized array.

As a result, Wasmtime language bindings based on the C API will need to be
updated once this change is pulled in.

Fixes #2211.
Fixes #2131.

* Update Doxygen comments for wasm.h changes.

crates/c-api/src/instance.rs

@@ -40,16 +40,15 @@ impl wasm_instance_t {
 pub unsafe extern "C" fn wasm_instance_new(
     store: &wasm_store_t,
     wasm_module: &wasm_module_t,
-    imports: *const Box<wasm_extern_t>,
+    imports: *const wasm_extern_vec_t,
     result: Option<&mut *mut wasm_trap_t>,
 ) -> Option<Box<wasm_instance_t>> {
     let mut instance = ptr::null_mut();
     let mut trap = ptr::null_mut();
-    let err = wasmtime_instance_new(
+    let err = _wasmtime_instance_new(
         store,
         wasm_module,
-        imports,
-        wasm_module.module().imports().len(),
+        (*imports).as_slice(),
         &mut instance,
         &mut trap,
     );
@@ -83,31 +82,27 @@ pub unsafe extern "C" fn wasm_instance_new(
 pub unsafe extern "C" fn wasmtime_instance_new(
     store: &wasm_store_t,
     module: &wasm_module_t,
-    imports: *const Box<wasm_extern_t>,
-    num_imports: usize,
+    imports: *const wasm_extern_vec_t,
     instance_ptr: &mut *mut wasm_instance_t,
     trap_ptr: &mut *mut wasm_trap_t,
 ) -> Option<Box<wasmtime_error_t>> {
-    _wasmtime_instance_new(
-        store,
-        module,
-        std::slice::from_raw_parts(imports, num_imports),
-        instance_ptr,
-        trap_ptr,
-    )
+    _wasmtime_instance_new(store, module, (*imports).as_slice(), instance_ptr, trap_ptr)
 }
 
 fn _wasmtime_instance_new(
     store: &wasm_store_t,
     module: &wasm_module_t,
-    imports: &[Box<wasm_extern_t>],
+    imports: &[Option<Box<wasm_extern_t>>],
     instance_ptr: &mut *mut wasm_instance_t,
     trap_ptr: &mut *mut wasm_trap_t,
 ) -> Option<Box<wasmtime_error_t>> {
     let store = &store.store;
     let imports = imports
         .iter()
-        .map(|import| import.which.clone())
+        .filter_map(|import| match import {
+            Some(i) => Some(i.which.clone()),
+            None => None,
+        })
         .collect::<Vec<_>>();
     handle_instantiate(
         Instance::new(store, module.module(), &imports),