xmlsecurity: fix Windows XP build

xmlsecurity/source/xmlsec/mscrypt/x509certificate_mscryptimpl.cxx(511) :
error C2065: ´CERT_SHA256_HASH_PROP_ID´ : undeclared identifier

Change-Id: I644d6797d81a506ca9b91d83eead16503af93905
Reviewed-on: https://gerrit.libreoffice.org/23494Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>

xmlsecurity/source/xmlsec/mscrypt/x509certificate_mscryptimpl.cxx

@@ -33,6 +33,11 @@
 #include <utility>
 #include <tools/time.hxx>
 
+// Needed only for Windows XP.
+#ifndef CERT_SHA256_HASH_PROP_ID
+#define CERT_SHA256_HASH_PROP_ID 107
+#endif
+
 using namespace com::sun::star;
 using namespace ::com::sun::star::uno ;
 using namespace ::com::sun::star::security ;