perf ui/gtk: Use struct perf_error_ops

perf ui/gtk: Use struct perf_error_ops

Define and use perf_gtk_eops to provide a GTK2 message dialog for error
reporting and a info_bar for warning.

As GtkInfoBar requires recent GTK+ libraries, provides a fallback
implementation using statusbar widget too.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338265382-6872-8-git-send-email-namhyung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>