Bump version to 1.13.20~.

ChangeLog

@@ -1,3 +1,7 @@
+2006-05-04  Guillem Jover  <guillem@debian.org>
+
+	* configure.ac: Bump version to 1.13.20~.
+
 2006-05-04  Guillem Jover  <guillem@debian.org>
 
 	* configure.ac: Release 1.13.19.