perf report: Add a popup menu to ask what operation is to be performed

Right now it presents a menu with these options:

 +------------------------------+
 | Annotate CURRENT_SYMBOL_NAME |
 | Exit                         |
 +------------------------------+

If the highlighted (current) symbol is not annotatable only the
"Exit" option will appear.

Also add a confirmation dialog when ESC is pressed on the top
level to avoid exiting the application by pressing one too many
ESC key.

To get to the menu just press the -> (Right navigation key), to
exit just press ESC.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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: <1269459619-982-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>