Revert "Don't mark async functions as hoist"

This reverts commit d34cb69912.

packages/babel-helper-remap-async-to-generator/src/index.js

@@ -87,6 +87,7 @@ function plainFunction(path: NodePath, callId: Object) {
         t.callExpression(container, [])
       )
     ]);
+    declar._blockHoist = true;
 
     retFunction.id = asyncFnId;
     path.replaceWith(declar);

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/statement/actual.js

@@ -1,5 +1,3 @@
-function normalFunction() {}
-
 async function foo() {
   var wat = await bar();
 }

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/statement/expected.js

@@ -1,5 +1,3 @@
-function normalFunction() {}
-
 let foo = function () {
   var ref = babelHelpers.asyncToGenerator(function* () {
     var wat = yield bar();