Noted by Guido:
Note in the "Caveats" section should refer to the exit() function, not
exit_thread().
diff --git a/Doc/lib/libthread.tex b/Doc/lib/libthread.tex
index dab7c89..652058d 100644
--- a/Doc/lib/libthread.tex
+++ b/Doc/lib/libthread.tex
@@ -108,7 +108,7 @@
\item
Calling \function{sys.exit()} or raising the \exception{SystemExit}
-exception is equivalent to calling \function{exit_thread()}.
+exception is equivalent to calling \function{exit()}.
\item
Not all built-in functions that may block waiting for I/O allow other