Fix imported memory fallback and add common stdlib imports to loader

lib/loader/tests/assembly/index.ts

@@ -60,3 +60,7 @@ export const varadd_ptr = varadd;
 export function calladd(fn: (a: i32, b: i32) => i32, a: i32, b: i32): i32 {
   return fn(a, b);
 }
+
+export function dotrace(num: f64): void {
+  trace("The answer is", 1, num);
+}

lib/loader/tests/index.js

@@ -59,3 +59,6 @@ assert.strictEqual(fn(2), 4);
 // should be able to create a new function and call it from WASM
 ptr = module.newFunction(module.varadd);
 assert.strictEqual(module.calladd(ptr, 2, 3), 5);
+
+// should be able to use trace
+module.dotrace(42);