Don't strip port number in sanitise_uri

sanitize_uri is used to translate URIs to pathnames in order to find
downloaded index files.

However, it had been stripping off the port number, while wget creates paths
that include the port number.  This means that if your URI includes a port
number, like http://example.com:8080/debian, wget would download files into a
directory named .../skel/example.com:8080/debian/, but apt-mirror would look
for the files in .../skel/example.com/debian/.

It looks like wget has done this for many years, and there's no easy way to
disable it.  You can have wget apply its own sanitization filters for
different platforms with --restrict-file-names but Unix mode includes the port
with a ":", and Windows mode replaces the ":" but also replaces other
characters which would mean adjusting sanitise_uri to match.  It seems like the
simplest way to be consistent with wget is to remove the port number filter
from sanitise_ui, since ":" is a valid component of a pathname and doesn't
seem to cause any issues.

Fixes #19

apt-mirror

@@ -485,7 +485,6 @@ sub sanitise_uri
     my $uri = shift;
     $uri =~ s[^(\w+)://][];
     $uri =~ s/^([^@]+)?@?// if $uri =~ /@/;
-    $uri =~ s&:\d+/&/&;                       # and port information
     $uri =~ s/~/\%7E/g if get_variable("_tilde");
     return $uri;
 }