<rdar://problem/15319880>

Introduce a new boolean setting enable-auto-oneliner
This setting if set to false will force LLDB to not use the new compact one-line display

By default, one-line mode stays on, at least until we can be confident it works.
But now if it seriously impedes your workflow while it evolves/it works wonders but you still hate it, there's a way to turn it off