RTFProducer overhaul

[Axel 'Mikesch' Katerbau]

Hi all,

the single most important GNUstep application is TextEdit.app for me. 
On Mac OS is use it all the time. To make another step to usefulness of 
GNUstep's TextEdit I did some work on RTFProducer (this is the code 
that generates RTF output from attributed strings). 


What is the right way to contribute the code I wrote?

Based on the work of Daniel Böhringer and Fred Kiefer I did the following:

OVERVIEW:
Works now on attribute deltas instead of 'local-paragraph attributes'.

DONE:
- fixed memory leaks
- optimized RTF output (reduces RTF file size dramatically)
- support for RTFD (text attachments)
- handling of non-ansi/ASCII characters
- tab stops (left, right, centered, decimal) now supported
- paragraph style indentation fixed
- fixed handling of text attributes like 'underline'

STILL MISSING:
- support for some text attributes (e.g. NSKernAttributeName)
- some things that I forgot to mention :-)

CAUTION:
- Not too much tested, but works quite well for me.
- Tested only for left-to-right text and with western characters (maybe 
someone would like to test it?) 

- GNUstep's RTF parser is quite incomplete (e.g. doesn't understand 
non-ascii characters) so the produced RTF output cannot be read by 
GNUstep without 'loss'. 


Tested on Mac OS X by letting Cocoa parse my RTF output (with the help 
of a simple test application). 

Also tested on GNUstep with TextEdit.app (with the restrictions 
mentioned above). 


Greetings from Cologne,
 Axel