Flipping url-show-status default

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

The url library is very chatty.  I think most users would get a more
pleasant experience if url-show-status defaulted to nil.  I mean, our
other network libraries don't issue tons of messages every time you
transfer data, so I don't really see why url fetching should be
different.

This would avoid flashing tons of these messages when you read
HTML-based news, for instance:

Reading [image/gif]... 52 bytes of 45 bytes (116%)
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%)
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%) [5 times]
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%)
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%)
Reading [text/plain]... 25 bytes of 15 bytes (167%)
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%)
Reading [text/plain]... 25 bytes of 15 bytes (167%)
Reading [text/html; charset=UTF-8]... 330 bytes of 321 bytes (103%)
Reading [text/plain]... 25 bytes of 15 bytes (167%)


-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen