Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.

diff -Naur --exclude=debian perl-5.8.8.orig/lib/Net/Config.pm perl-5.8.8/lib/Net/Config.pm
--- perl-5.8.8.orig/lib/Net/Config.pm	2002-03-01 01:04:31.000000000 +1100
+++ perl-5.8.8/lib/Net/Config.pm	2006-02-03 00:00:55.000000000 +1100
@@ -57,9 +57,8 @@
 }
 TRY_INTERNET_CONFIG
 
-my $file = __FILE__;
+my $file = '/etc/perl/Net/libnet.cfg';
 my $ref;
-$file =~ s/Config.pm/libnet.cfg/;
 if ( -f $file ) {
     $ref = eval { local $SIG{__DIE__}; do $file };
     if (ref($ref) eq 'HASH') {