Modernise 'selfsign.c' to use new X509_NAME code

and add example of extension aliasing. Also fix
the extension aliasing because it didn't work :-)

crypto/x509v3/v3_lib.c

@@ -132,7 +132,7 @@ int X509V3_EXT_add_alias(int nid_to, int nid_from)
 	*tmpext = *ext;
 	tmpext->ext_nid = nid_to;
 	tmpext->ext_flags |= X509V3_EXT_DYNAMIC;
-	return 1;
+	return X509V3_EXT_add(tmpext);
 }
 
 void X509V3_EXT_cleanup(void)