gdb-remote tests: added test to verify thread stop info when multi-threaded app is interrupted.

The Linux version is marked XFAIL for the moment, fixing next.

Related to http://llvm.org/bugs/show_bug.cgi?id=20908.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@217613 91177308-0d34-0410-b5e6-96231b3b80d8