fixup! Don't atoi off the end of a buffer chunk.

Credit AFL in the changes file.

changes/bug20894

@@ -3,6 +3,7 @@
       do not read off the end of the buffer. This bug was a potential
       remote denial-of-service attack against Tor clients and relays.
       A workaround was released in October 2016, which prevents this
-      bug from crashing Tor.  This is a fix for the underlying issue,
+      bug from crashing Tor. This is a fix for the underlying issue,
       which should no longer matter (if you applied the earlier patch).
-      Fixes bug 20894; bugfix on 0.2.0.16-alpha.
+      Fixes bug 20894; bugfix on 0.2.0.16-alpha. Bug found by fuzzing
+      using AFL (http://lcamtuf.coredump.cx/afl/).