saving attachments in separate directories

I just commited the change to parse.c (and a tiny one to setup.h) that makes it store all attachments in separate directories.

It now saves the files in 'att-<num>' which is first cleared from any possible previous contents (like if you run hypermail several times on the same target dir without manually removing the files first).

-- 
             Daniel Stenberg - http://www.fts.frontec.se/~dast
   ech`echo xiun|tr nu oc|sed 'sx\([sx]\)\([xoi]\)xo un\2\1 is xg'`ol