When we detect a stack unwind loop, before we abort
the backtrace, try falling back to the architecture default
unwind plan and see if we can backtrace a little further.
<rdar://problem/18556719> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@219247 91177308-0d34-0410-b5e6-96231b3b80d8