[wasm] Implement correct 2-level namespace for imports.

test/mjsunit/wasm/receiver.js

Index: test/mjsunit/wasm/receiver.js
diff --git a/test/mjsunit/wasm/receiver.js b/test/mjsunit/wasm/receiver.js
index 97a6d94c9bc6305f7ddb8f7738d82bd5d5b79a4d..b3373c11ec0ed69636028bfec00477e1d2c668b0 100644
--- a/test/mjsunit/wasm/receiver.js
+++ b/test/mjsunit/wasm/receiver.js
@@ -11,7 +11,7 @@ function testCallImport(func, expected, a, b) {
   var builder = new WasmModuleBuilder();
 
   var sig_index = builder.addType(kSig_i_dd);
-  builder.addImport("func", sig_index);
+  builder.addImport("mod", "func", sig_index);
   builder.addFunction("main", sig_index)
     .addBody([
       kExprGetLocal, 0,            // --
@@ -19,7 +19,7 @@ function testCallImport(func, expected, a, b) {
       kExprCallFunction, 0])         // --
     .exportAs("main");
 
-  var main = builder.instantiate({func: func}).exports.main;
+  var main = builder.instantiate({mod: {func: func}}).exports.main;
 
   assertEquals(expected, main(a, b));
 }