Add NEWS entry [ci skip]
diff --git a/NEWS.rst b/NEWS.rst
index c862424..ae278fd 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -1,3 +1,7 @@
+- [varLib] Fixed merging of class-based kerning. Before, the process could introduce
+  rogue kerning values and variations for random classes against class zero (everything
+  not otherwise classed).
+
 3.42.0 (released 2019-05-28)
 ----------------------------