applied patch from ticket #86142: Missing XML declaration in request

https://rt.cpan.org/Public/Bug/Display.html?id=86142
tests still pass, so, good enough, right?

lib/SOAP/WSDL/Serializer/XSD.pm

@@ -30,7 +30,7 @@ sub serialize {
     my $soap_prefix = $opt->{ namespace }->{ $SOAP_NS };
 
     # envelope start with namespaces
-    my $xml = "<$soap_prefix\:Envelope ";
+    my $xml = qq|<?xml version="1.0" ?><$soap_prefix\:Envelope |;
 
     while (my ($uri, $prefix) = each %{ $opt->{ namespace } })
     {