[javascript] Support for-of loop

[hudec117]

Affects PMD Version:

6.22.0

Description:

The for-of loop is recognised incorrectly as an "EmptyStatement".

That's an ES6 / ECMAScript 2015 feature.

It seems to be partially supported by Rhino: http://mozilla.github.io/rhino/compat/engines.html

Code Sample demonstrating the issue:

// Generates "ForInLoop" in AST
for (var item in items) {}

// Generate "EmptyStatement" in AST
for (var item of items) {}
for (let item of items) {}
for (const item of items) {}

Steps to reproduce:

1. Start PMD Designer
2. Set language to Ecmascript
3. Copy-paste code sample from above
4. Observe AST for incorrect "EmptyStatement"

Running PMD through: Designer

Related issues: #2305 #1235 #699