feat(c-api) Implement wasm_module_name and wasm_module_set_name.

I submited a proposal to the official `wasm.h` by the way,
WebAssembly/wasm-c-api#157. For the moment,
let's keep that as a vendor specific implementation.

lib/c-api/src/wasm_c_api/wasmer.rs

@@ -1,9 +1,35 @@
 //! Wasmer-specific extensions to the Wasm C API.
 
-use crate::wasm_c_api::instance::wasm_instance_t;
+use super::instance::wasm_instance_t;
+use super::module::wasm_module_t;
+use super::types::wasm_name_t;
 use std::ffi::c_void;
+use std::str;
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_instance_get_vmctx_ptr(instance: &wasm_instance_t) -> *mut c_void {
     instance.inner.vmctx_ptr() as _
 }
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_module_name(module: &wasm_module_t, out: &mut wasm_name_t) {
+    let name = match module.inner.name() {
+        Some(name) => name,
+        None => return,
+    };
+
+    *out = name.as_bytes().to_vec().into();
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_module_set_name(module: &wasm_module_t, name: &wasm_name_t) -> bool {
+    let name = match name.into_slice() {
+        Some(name) => match str::from_utf8(name) {
+            Ok(name) => name,
+            Err(_) => return false, // not ideal!
+        },
+        None => return false,
+    };
+
+    module.inner.set_name(name)
+}