Xnamespace: fix wrong const char* authProto

The authProto field always is assigned to dynamically allocated buffer
(strdup()'ed) and needs to be freed sometimes, so cannot be const.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

Xext/namespace/namespace.h

@@ -12,7 +12,7 @@
 
 struct auth_token {
     struct xorg_list entry;
-    const char *authProto;
+    char *authProto;
     char *authTokenData;
     size_t authTokenLen;
     XID authId;