perf top: Live TUI Annotation

Now one has just to press the right key, 'a' or Enter on the main 'perf
top --tui' screen to live annotate the symbol under the cursor.

The annotate window starts centered on the hottest line (the one with
most samples so far) then TAB and shift+TAB can be used to go to the
prev/next hot line.

Pressing 'H' at any point will center again the screen on the hottest
line.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/top.h

@@ -44,6 +44,7 @@ struct perf_top {
 	pid_t		   target_pid, target_tid;
 	bool		   hide_kernel_symbols, hide_user_symbols, zero;
 	const char	   *cpu_list;
+	struct sym_entry   *sym_filter_entry;
 	struct perf_evsel  *sym_evsel;
 };