criu --help: rectify --cpu-cap

It is somewhat hard to fully describe --cpu-cap in --help output,
but let's at least say that:
 - option is used to either write or check capabilities;
 - the argument is a comma-separated list;
 - empty argument means "all".

Also, while saying it, contain ourselves within 80 columns of output.

The last item requires more work of course. I'm not sure about others,
but I often work in terminals which are 80 columns wide, and non-wrapped
output looks pretty ugly. I mean, we surely can be better than 'adp'.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/crtools.c

@@ -820,8 +820,9 @@ usage:
 "     --pidfile FILE     write root task, service or page-server pid to FILE\n"
 "  -W|--work-dir DIR     directory to cd and write logs/pidfiles/stats to\n"
 "                        (if not specified, value of --images-dir is used)\n"
-"     --cpu-cap [CAP]    require certain cpu capability. CAP: may be one of:\n"
-"                        'cpu','fpu','all','ins','none'. To disable capability, prefix it with '^'.\n"
+"     --cpu-cap [CAP]    CPU capabilities to write/check. CAP is comma-separated\n"
+"                        list of: cpu, fpu, all, ins, none. To disable\n"
+"                        a capability, use ^CAP. Empty argument implies all.\n"
 "     --exec-cmd         execute the command specified after '--' on successful\n"
 "                        restore making it the parent of the restored process\n"
 "  --freeze-cgroup\n"