Tests whether there is a variable declaration accessible to the current
scope, ie including parent scope

@param name
@returns {Boolean}
function(name) {
      var pos = name.indexOf(".");
      if (pos > -1) {
        name = name.substring(0, pos); 
      }
      for (var tmp = this.__scope; tmp; tmp = tmp.parent) {
        if (tmp.vars[name] !== undefined) {
          return true; 
        } 
      }
      return false;
    }