XML/RPC refomatting & file splitting

Hi, 

I've started to reformate RPC.php - it may be genius code but it's
widely undocumented and hard to read. I replaced the tabs with spaces
and added basic inline docs the author or someone else who knows the
code can complete. Finally I put every class into it's own file. "One
class per file" is a good old Java coding rule. PHPDoc needs it like
JavaDoc does. 

I might have broken the code, don't know how to test it. Is there
anybody that can help me with it? If not I'd have a strange feeling with
the commit... Thanks!

Ulf