Ensure toolbar places itself correctly even with auto-hiding menu bar

[uliwitness]

10.11 supports turning off the menu bar system wide. The toolbar should at the least slide up in that case. Ideally, it would also slide out of the way as the menu bar shows, like toolbars of fullscreen windows do.

[uliwitness]

Note: We're in the process of rewriting the toolbar in Hammer itself. So don't spend too much time on that side of things. Instead, just getting notifications when the menu bar shows/hides and where its bottom is would be the important part. If hooking it up to the old toolbar is more involved than calling setFrameOrigin: on the window, don't bother.