Bug 924916: Part 1 - Implement OS.File.setDates() for Unix. r=yoric
Bug 924916: Part 2 - Implement OS.File.setDates() for Windows. r=yoric
Bug 924916: Part 3 - Provide async OS.File.setDates() API for main-thread. r=yoric
Bug 924916: Part 4 - xpcshell tests for OS.File.setDates(). r=yoric