urlsum.txt: summary of results
   urllog.txt: log of progress
   urlok.html: found 586 urls: were ok
urlmoved.html: ----- 115 urls: moved
 urlhost.html: ERROR  48 hosts: failed
 urlfail.html: ERROR 121 urls: failed
urlfailX.html: ERROR 121 urls: failed (cross referenced)
urlfailF.html: ERROR  16 files with failed urls
 urlskip.html: warn   10 urls: not checked
urlwarnF.html: warn    1 url with warnings