fix: add use warnings to all production modules

Parser.pm

@@ -9,6 +9,7 @@
 package XML::Parser;
 
 use strict;
+use warnings;
 
 our ( $VERSION, $LWP_load_failed );
 

Parser/Style/Debug.pm

@@ -2,6 +2,7 @@
 
 package XML::Parser::Style::Debug;
 use strict;
+use warnings;
 
 sub Start {
     my $expat = shift;

Parser/Style/Objects.pm

@@ -2,6 +2,7 @@
 
 package XML::Parser::Style::Objects;
 use strict;
+use warnings;
 
 sub Init {
     my $expat = shift;

Parser/Style/Stream.pm

@@ -2,6 +2,7 @@
 
 package XML::Parser::Style::Stream;
 use strict;
+use warnings;
 
 # This style invented by Tim Bray <tbray@textuality.com>
 

Parser/Style/Subs.pm

@@ -2,6 +2,7 @@
 
 package XML::Parser::Style::Subs;
 use strict;
+use warnings;
 
 sub Start {
     no strict 'refs';

Parser/Style/Tree.pm

@@ -2,6 +2,7 @@
 
 package XML::Parser::Style::Tree;
 use strict;
+use warnings;
 
 sub Init {
     my $expat = shift;