Wrong default value breaks account creation

The default value for the 'user_register' variable used throughout user.module is '1', which means users are allowed to register for accounts. fbconnect, however, assumes a default value of '0', which breaks account creation using Facebook, as long as the user settings haven't been manually saved (since then the value '1' will be saved to the variables table). The attached patch fixes the code to respect user-module defaults.