[development] Improving theme('username') with inspiration from Facebook

[Robert Douglass]

I find these to be interesting and possibly very compelling additions. 
Even if not every language will be able to utilize the flags, those 
languages can simply fall back on current default behavior. Languages 
that can leverage the flags will be able to provide a richer experience. 
Plus, adopting elements of the fb API might make it one small step 
easier to write fb applications. At this point it should be pretty clear 
to everybody that this is an important part of Drupal's future.