criu --help: reformat -v description

Let's save 4 lines of output and put -vvv at the same line as -v 3.

Also, -v argument is in fact option, so mark it as such: [NUM]
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -390,16 +390,12 @@ usage:
 "* Logging:\n"
 "  -o|--log-file FILE    log file name (path is relative to --images-dir)\n"
 "     --log-pid          enable per-process logging to separate FILE.pid files\n"
-"  -v NUM                set logging level\n"
-"                          0 - messages regardless of log level\n"
-"                          1 - errors, when we are in trouble\n"
-"                          2 - warnings (default)\n"
-"                          3 - informative, everything is fine\n"
-"                          4 - debug only\n"
-"  -v             same as -v 1\n"
-"  -vv            same as -v 2\n"
-"  -vvv           same as -v 3\n"
-"  -vvvv          same as -v 4\n"
+"  -v [NUM]              set logging level:\n"
+"                          -v 0        - messages regardless of log level\n"
+"                          -v 1, -v    - errors, when we are in trouble\n"
+"                          -v 2, -vv   - warnings (default)\n"
+"                          -v 3, -vvv  - informative, everything is fine\n"
+"                          -v 4, -vvvv - debug only\n"
 "\n"
 "Page server options\n"
 "  --page-server         send pages to page server (for 'dump' command)\n"