BiDi patch

[Tomas Frydrych]

I have now added logic that ensures that ltr-only lines bypass the 
BiDi algorithm and rtl-only lines get a faster treatment then full BiDi 
lines. This means that the BiDi functionality could be added to the 
main-stream build without significant impact on performance for 
non-bidi documents. The latest patch though still treats the BiDi 
support as a compile time option.

The patch can be found on the usual place 
(www.frydrych.uklinux.net/abi/)

Tomas