Limit VNC size by default.

lib/util/cliutil.js

@@ -2,6 +2,11 @@ module.exports.list = function(val) {
   return val.split(/\s*,\s*/g).filter(Boolean)
 }
 
+module.exports.size = function(val) {
+  var match = /^(\d+)x(\d+)$/.exec(val)
+  return match ? [+match[1], +match[2]] : undefined
+}
+
 module.exports.allUnknownArgs = function(args) {
   return [].slice.call(args, 0, -1).filter(Boolean)
 }