perf tools: change machine__findnew_thread() to set thread pid

Add a new parameter for 'pid' to machine__findnew_thread().
Change callers to pass 'pid' when it is known.

Note that callers sometimes want to find the main thread
which has the memory maps.  The main thread has tid == pid
so the usage in that case is:

	machine__findnew_thread(machine, pid, pid)

whereas the usage to find the specific thread is:

	machine__findnew_thread(machine, pid, tid)

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1377591794-30553-2-git-send-email-adrian.hunter@intel.com


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