Adjust the calls to __introspection_dispatch_thread_get_item_info to
use a system-wide unique thread ID instead of a pthread_t to identify
the thread we want debug info for.  Also, free some more memory regions
that needed to be freed.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@201117 91177308-0d34-0410-b5e6-96231b3b80d8