perf newt: Add a "Zoom into foo.so DSO" and reverse operations

Clicking on -> will bring as one of the popup menu options a "Zoom into
CURRENT DSO", i.e. CURRENT will be replaced by the name of the DSO in
the current line.

Choosing this option will filter out all samples that didn't took place
in a symbol in this DSO.

After that the option reverts to "Zoom out of CURRENT DSO", to allow
going back to the more compreensive view, not filtered by DSO.

Future similar operations will include zooming into a particular thread,
COMM, CPU, "last minute", "last N usecs", etc.

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.h

@@ -48,7 +48,8 @@ struct hist_entry {
 	struct map_symbol	ms;
 	u64			ip;
 	char			level;
-	struct symbol	  *parent;
+	bool			filtered;
+	struct symbol		*parent;
 	union {
 		unsigned long	  position;
 		struct hist_entry *pair;