Patch by Roman Tereshonkov and Kari Hautio for rdiff-backup <= 1.2.8 to avoid a build failure with
librsync >= 1.0.0 (which is a security bugfix release). The discussion and solution finding can be
found at https://bugs.launchpad.net/duplicity/+bug/1416344 (for duplicity).

--- rdiff-backup-1.2.8/_librsyncmodule.c			2009-03-16 15:36:21.000000000 +0100
+++ rdiff-backup-1.2.8/_librsyncmodule.c.librsync-1.0.0		2015-03-02 00:54:24.000000000 +0100
@@ -59,8 +59,13 @@
   if (sm == NULL) return NULL;
   sm->x_attr = NULL;
 
+#ifdef RS_DEFAULT_STRONG_LEN
   sm->sig_job = rs_sig_begin((size_t)blocklen,
 							 (size_t)RS_DEFAULT_STRONG_LEN);
+#else
+  sm->sig_job = rs_sig_begin((size_t)blocklen,
+							 (size_t)8, RS_MD4_SIG_MAGIC);
+#endif
   return (PyObject*)sm;
 }