[[FIX]] Tolerate late definition of async function

We used to mark `async function` as unreachable instead of treating it
as any other late function definition. This change makes jshint react to
`async` keyword in the same way as it reacted to `function` keyword.

src/jshint.js

@@ -1851,7 +1851,7 @@ var JSHINT = (function() {
         return;
       }
       if (t.id !== "(endline)") {
-        if (t.id === "function") {
+        if (t.id === "function" || t.id === "async") {
           if (state.option.latedef === true) {
             warning("W026", t);
           }

tests/unit/parser.js

@@ -8267,6 +8267,21 @@ exports.unreachable = {
     TestRun(test)
       .test(src);
 
+    test.done();
+  },
+  'async function': function (test) {
+    var src = [
+      "(function() {",
+      "  return f(4);",
+      "  async function f(p) {",
+      "    return p + 1;",
+      "  }",
+      "}());"
+    ];
+
+    TestRun(test)
+      .test(src, { esversion: 8, latedef: 'nofunc' });
+
     test.done();
   }
 };