Add new command 's' to modify the update interval. Limited to a maximum of
25.5 sec and a minimum of 0.1 sec, since curses cannot handle longer
and shorter delays respectively.
Signed-off-by: NStefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>