Update ABI version as discussed with sustrik
diff --git a/src/nn.h b/src/nn.h
index 77f8327..e64266b 100644
--- a/src/nn.h
+++ b/src/nn.h
@@ -71,13 +71,13 @@
/* www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html */
/* The current interface version. */
-#define NN_VERSION_CURRENT 1
+#define NN_VERSION_CURRENT 2
/* The latest revision of the current interface. */
#define NN_VERSION_REVISION 0
/* How many past interface versions are still supported. */
-#define NN_VERSION_AGE 1
+#define NN_VERSION_AGE 2
/******************************************************************************/
/* Errors. */
