Release 2.0 beta 1

Even though alpha started at 0, we release beta 1 first as we did for
1.2.

Reviewed-by: imsnah, ultrotter

configure.ac

@@ -2,7 +2,7 @@
 m4_define([gnt_version_major], [2])
 m4_define([gnt_version_minor], [0])
 m4_define([gnt_version_revision], [0])
-m4_define([gnt_version_suffix], [~alpha1])
+m4_define([gnt_version_suffix], [~beta1])
 m4_define([gnt_version_full],
           m4_format([%d.%d.%d%s],
                     gnt_version_major, gnt_version_minor,