Clarify Cachegrind changes


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2495 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/NEWS b/NEWS
index 00825ed..b24f6dc 100644
--- a/NEWS
+++ b/NEWS
@@ -96,7 +96,9 @@
   in the soft limit causing assertions when valgrind tries to allocate
   descriptors from the reserved area.
 
-* Major overhaul of Cachegrind implementation (not user-visible)
+* Major overhaul of Cachegrind implementation.  Only user visible change
+  is that cachegrind.out files are now typically 90% smaller than they
+  used to be.  Code annotation times are correspondingly much smaller.
 
 * Client requests for telling valgrind about memory pools.