Incorrectly renaming nested object literals

[dariajung]

/// <reference path ='../../typings/source-map/source-map.d.ts' />
import SourceMap = require('source-map');

var x: SourceMap.Mapping = {
    original: { line: 0, column: 0 },
    generated: { line: 0, column: 0 },
    source: ''
}

line and column are incorrectly being renamed. They are of type SourceMap.Position.

Some of the work to address this is on branch: https://github.com/angular/ts-minify/tree/nested-obj-literals.