Add a new SBThread::GetQueue() method to get the queue that is 
currently associated with a given thread, on relevant targets.

Change the queue detection code to verify that the queues 
associated with all live threads are included in the list.
<rdar://problem/16411314> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@207160 91177308-0d34-0410-b5e6-96231b3b80d8