[PATCH] tabwidth inconsistency

Hello,

regarding the following TODO item:

o  tabwidth is static in page.c but when toggling it to 4 and opening
    another article the article is cooked with width 8 (hardcoded in
    art_open()) and the next toggle message is wrong.
    [20090320 Urs Janssen <[email protected]>]

I see two possible solutions:

1. tabwidth is valid per article. Opening an article sets tabwidth to  
8 and one can toggle to 4 and back to 8. Opening another article  
resets tabwidth to 8 and one can toggle to 4 and back again.

2. tabwidth is valid per tin session. The initial value is 8. After  
toggeling to 4 this is valid for all further articles until one  
toggles back to 8. Then, 8 is valid for all further article and so on.

The attached patch implements #2 (I kept the fixed tabwidth of 8 in  
help pages and verbatim blocks).

If #1 is peferred I can send in another patch.

Dennis