- jslint-ecma - Add ES2015-feature for..of.

[kaizhu256]

Fixes #176.

A sorely missed feature, that happily is now implemented :)

// for-of statement using const or let now passes jslint w/o warnings
(function for_loop() {
    for (const [ // full destructure support
        {
            cc,
            dd = 0,
            dd: ee,
            ee: [{bb}],
            ...aa
        },
        [
            gg,
            ...ff
        ]
    ] of for_loop) {
        aa(bb, cc, dd, ee, ff, gg);
    }

    // traditional for(;;) statement using let is now allowed
    for (let aa = 0; aa < 8; aa += 1) {
        String(aa);
    }
}());

under-the-hood, jslint's scoping system was significantly revamped

- by adding block-level scoping for:
    - `const`, `let`, and `declared-function-name`.
- in order to integrate normal variable-declaration-logic into for-loop variables.

a beneficial side-effect, is that const and let declarations can be declared inside the top of statement-blocks,

- instead of top of function-block or script, e.g.:

/*jslint beta*/
function foo() {
    var aa = 0; // var statement still required to be at top of function
    ...
    if (aa) {
        let bb = 1; // let statement can now be inside the top of a block
        ...
    } else {
        const bb = 2; // const statement can now be inside the top of a block
                      // and won't complain about name-collision from previous block
        ...
    }
}

following special variables / parameters / names are declared inside a hidden scope to avoid name-collision with normal variables:

- catch-variable
- for-variable
- function-parameter
- label-name

This PR will:

• jslint-ecma - Add ES2015-feature for..of.

This PR will additionally:

• jslint - Disable directive-option /jslint for/, replacing it with for-loop specific warnings.
• jslint - Update scope-related warnings for variables, depending on whether they are let/const (scope_block) or var (scope_function).
• jslint - Change scope from scope_function to scope_block:
  • const-declaration
  • let-declaration
  • function-declaration
• jslint - Add implicit scope_block for:
  • do-while
  • for-loop
  • if-else
  • while-loop
• jslint - Add hidden scope_block for:
  • catch-variable
  • for-variable
  • function-parameter
  • label-name
• jslint - Restrict scope from scope_function to its own function-body:
  • named-function-expression
• jslint - Rename internal scope-variables to imporove readability of scope-logic:
  • 'blockage' to 'scope_block'
  • 'functionage' to 'scope_function'
• jslint - Add block-scope to internal-function jslint_phase3_parse().