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	2006-11-19 01:21:53.000000000 +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') {
@@ -131,8 +130,8 @@
 C<Net::Config> holds configuration data for the modules in the libnet
 distribuion. During installation you will be asked for these values.
 
-The configuration data is held globally in a file in the perl installation
-tree, but a user may override any of these values by providing their own. This
+The configuration data is held globally in C</etc/perl/Net/libnet.cfg>,
+but a user may override any of these values by providing their own. This
 can be done by having a C<.libnetrc> file in their home directory. This file
 should return a reference to a HASH containing the keys described below.
 For example
