perf tools: Add dedicated unwind addr_space member into thread struct

Milian reported issue with thread::priv, which was double booked by perf
trace and DWARF unwind code. So using those together is impossible at
the moment.

Moving DWARF unwind private data into separate variable so perf trace
can keep using thread::priv.

Reported-and-Tested-by: Milian Wolff <milian.wolff@kdab.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andreas Hollmann <hollmann@in.tum.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1460013073-18444-2-git-send-email-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>