wasm: switch emulator to node.js

Unfortunately, the olin/cwa emulator does not handle floats correctly.
Node.js does, and because it is also supported by the Go WebAssembly
implementation it has better support in general.

targets/wasm.json

@@ -12,5 +12,5 @@
 	"ldflags": [
 		"-allow-undefined"
 	],
-	"emulator":      ["cwa"]
+	"emulator":      ["node", "targets/wasm_exec.js"]
 }

targets/wasm_exec.js

@@ -427,7 +427,6 @@
 				if (code === 0 && !go.exited) {
 					// deadlock, make Go print error and stack traces
 					go._callbackShutdown = true;
-					go._inst.exports.run();
 				}
 			});
 			return go.run(result.instance);