partial rtl support

I have checked in some changes that were languishing on the rtl-support branch.

0) I am using pyfribidi2 as the interface to the fribidi support library. If 
it's wanted and not available then a warning is issued by the code in textobject.py.

1) A new rl_settings option of rtlSupport (default 0) has been added to prevent 
trying to import pyfribidi2 when it's not wanted.

2) I added a test in tests/test_paragraph.py, however, my fonts aren't really up 
to the job of showing me decent output for the Arabic case at least. Seems that 
we need the ligatures near \ufebc which I don't seem to have; anyhoo my  Arabic 
/ Hebrew is not up to the job of deciding whether pyfribidi is doing its job 
properly.

3) It's not clear to me whether we should attempt to fix the many textual 
interfaces present inside reportlab or whether we should have a more generic 
string concept for use in those situations. Currently only the standard 
paragraph is doing the right thing (allegedly).

Any interested parties will need libfribidi / fribidi.dll and pyfribidi2.so/pyd 
to make headway.
-- 
Robin Becker