Curl_cookie_add: handle IPv6 hosts

1 - don't skip host names with a colon in them in an attempt to bail out
on HTTP headers in the cookie file parser. It was only a shortcut anyway
and trying to parse a file with HTTP headers will still be handled, only
slightly slower.

2 - don't skip domain names based on number of dots. The original
netscape cookie spec had this oddity mentioned and while our code
decreased the check to only check for two, the existing cookie spec has
no such dot counting required.

Bug: http://curl.haxx.se/bug/view.cgi?id=1221
Reported-by: Stefan Neis