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+  o Minor features (infrastructure):
+    - Tor now includes an improved timer backend, so that we can efficiently
+      support tens or hundreds of thousands of concurrent timers, as will be
+      needed for some of our planned anti-traffic-analysis work. This code
+      is based on William Ahern's "timeout.c" project, which implements
+      a "tickless hierarchical timing wheel". Closes ticket #18365.
+