perf gtk/hists: Set rules hint for the hist browser

perf gtk/hists: Set rules hint for the hist browser

The 'rules' means that every second line of the tree view has a shaded
background, which makes it easier to see which cell belongs to which
row in the tree view.  It can be useful for a tree view that has a lot
of rows.

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
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/1370337737-30812-7-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>