perf ui gtk: Implement ui_progress functions

Implement progress update function for GTK2 front end.

Note that since it will be called before gtk main loop so that we should
call gtk event loop handler directly.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1352813436-14173-3-git-send-email-namhyung@kernel.org


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