perf hists browser: Honour the help line provided by builtin-{top,report}.c

The hists_browser was replacing whatever helpline provided by 'top' or
'report' with a static "Press '?' for help on key bindings", fix it.

Now the message passed by top appears at the bottom of the screen:

"For a higher level overview, try: perf top --sort comm,dso"

As well the message that will be added when the user presses 'f' to
disable the events, something along the lines of "press f again to
re-enable...".

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-dacaja70mbfz3a0yj1n180gx@git.kernel.org


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