Update ChangeLog for 4.0.2.
diff --git a/ChangeLog b/ChangeLog
index fb376b2..58e4462 100644
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+++ b/ChangeLog
@@ -4,7 +4,9 @@
 
     https://github.com/jemalloc/jemalloc
 
-* 4.0.2 (XXX)
+* 4.0.2 (September 21, 2015)
+
+  This bugfix release addresses a few bugs specific to heap profiling.
 
   Bug fixes:
   - Fix ixallocx_prof_sample() to never modify nor create sampled small