<rdar://problem/12786725>

If there is any alive process being debugged, the user is asked for confirmation before quitting LLDB
This should prevent situations where the user mistakenly types "q" and LLDB slaughters their process without any mercy whatsoever
Since it can quickly get tedious, there is a new setting on the command interpreter to disable this and replicate the previous behavior

llvm-svn: 172757