[PATCH] '-G' & 'G' (getart_limit) corrections

Hi,

the attached patch deals with this TODO entry:

o  -G doesn't "work" in the !NNTP case, shall we disallow it in that  
case
    or shall we try to implement it?
    [20030421 Urs Janssen <[email protected]>]

'-G' and 'G' at group-level only work in the NNTP case with  
tinrc.cache_overview_files OFF. Reading overview data in  
art.c:read_overview() has ignored getart_limit. Now it works in the  
NNTP case with or without cache_overview_files and in the !NNTP case  
(local spool).

I've removed the TODO above read_art_headers() in art.c:index_group 
(), because last_read_article has nothing to do with min.  
last_read_article is the last article with valid header informations,  
setting this to min would cause read_art_header() to read in already  
present informations.

In addition, newsrc.c:grp_mark_read() now does what the description  
says, clear the bitmap only if art == NULL.

Dennis