Implement more granular cluster-merging

TODO: Documentation.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=71445
diff --git a/NEWS b/NEWS
index d985427..a5ac906 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,11 @@
+
+- Removed HB_NO_MERGE_CLUSTERS hack.
+- New API:
+  hb_buffer_cluster_level_t enum
+  hb_buffer_get_cluster_level()
+  hb_buffer_set_cluster_level()
+  hb-shape / hb-view --cluster-level
+
 Overview of changes leading to 0.9.41
 Thursday, June 18, 2015
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