[[FIX]] Init block bindings in C-style for loop

Previously, the `noin` production parameter was interpreted as an
indication of a `for/in` or `for/of` loop. This is incorrect because the
production parameter will also be set in the context of a C-style `for`
loop.

Ensure that block-scoped bindings are initialized sequentially for
C-style `for` loops.

src/jshint.js

@@ -4334,7 +4334,7 @@ var JSHINT = (function() {
       // Bindings are not immediately initialized in for-in and for-of
       // statements. As with `const` initializers (described above), the `for`
       // statement parsing logic includes
-      if (!noin) {
+      if (state.tokens.next.value !== "in" && state.tokens.next.value !== "of") {
         for (t in tokens) {
           if (tokens.hasOwnProperty(t)) {
             t = tokens[t];

tests/unit/core.js

@@ -2327,3 +2327,14 @@ exports["TDZ within for in/of head"] = function(test) {
 
   test.done();
 };
+
+// regression test for gh-3370
+exports.initializeCStyle = function(test) {
+  TestRun(test)
+    .test([
+      "for (let x, y = x; ;) {}",
+      "for (const x = 0, y = x; ;) {}"
+    ], { esversion: 6 });
+
+  test.done();
+};