[XeTeX] bidi loading settings

[Juan Acevedo]

Dear Vafa (and maybe others)

Since bidi is such a comprehensive package, I wonder is there is a way to load it selectively, I mean asking for some of the files not to be loaded, like 
book-xetex-bidi.def
This could help debug package conflicts, and maybe it would thus make possible some otherwise impossible combinations (like bidi & titlesec, if you see my point :-)

Thanks in advance
Juan