Deep clone diagnostic objects

[spahnke]

Fixes microsoft/monaco-editor#2392

Before this change the ts.Diagnostic objects internal to TypeScript were mutated. This was fine when the file property was cleared completely, but broke with #74 where we kept the fileName. The method computeLineStarts in typescriptServices.js then gets a parameter which is undefined (the source text of the file) causing the exception in the issue.

I tested with the code from the issue, the use-case from #74 and the original use-case from #48.

~line 8874 in out/amd/lib/typescriptServices.js

function computeLineStarts(text) { // text is now undefined
        var result = new Array();
        var pos = 0;
        var lineStart = 0;
        while (pos < text.length) {
            var ch = text.charCodeAt(pos);
            pos++;
            switch (ch) {
                case 13 /* carriageReturn */:
                    if (text.charCodeAt(pos) === 10 /* lineFeed */) {
                        pos++;
                    }
                // falls through
                case 10 /* lineFeed */:
                    result.push(lineStart);
                    lineStart = pos;
                    break;
                default:
                    if (ch > 127 /* maxAsciiCharacter */ && isLineBreak(ch)) {
                        result.push(lineStart);
                        lineStart = pos;
                    }
                    break;
            }
        }
        result.push(lineStart);
        return result;
    }

[alexdima]

Thank you!