Take comments into account when tracking sourcemap spans

[DanielRosenwasser]

This PR fixes #1980.

This is an alternative to PR #2014.

---

Rather than fixing up each use site to choose between how to emit, we create a common path that understands the sourcemap/comment ordering.

We now have 4 functions:

• emit - emits a node with sourcemap info and comments if appropriate
• emitNodeWithoutSourceMap - emits a node with only comment info
• emitVerbatimDeclarationName - emits a node with sourcemaps/comments without renaming if it is an identifier
• emitNodeWorker - emits a node with comments if appropriate, and takes a flag indicating whether or not to track sourcemaps. This is only called by the above two functions.

[JsonFreeman]

👍

[NN---]

This doesn't fix the issue.
It is easy to reproduce using this simple TS and HTML.

module Q {
    function P() {
        // Test this
        var a = 1;
    }
}

Running tsc --sourceMap produces the following files

var Q;
(function (Q) {
    function P() {
        // Test this
        var a = 1;
    }
})(Q || (Q = {}));
//# sourceMappingURL=a.js.map

a.js.map:

{"version":3,"file":"a.js","sourceRoot":"","sources":["a.ts"],"names":["Q","Q.P"],"mappings":"AAAA,IAAO,CAAC,CAKP;AALD,WAAO,CAAC,EAAC,CAAC;IACNA;QAEIC,AADAA,YAAYA;YACRA,CAACA,GAAGA,CAACA,CAACA;IACdA,CAACA;AACLD,CAACA,EALM,CAAC,KAAD,CAAC,QAKP"}

Now open this HTML in FF or Chrome , and you can still put a breakpoint on the comment.