JP 16: [thread.sharedtimedmutex.class] Add missing 'or' at end of

bullet.

Fixes #375.

Author: zygoloid

source/threads.tex

@@ -1560,7 +1560,7 @@
 The behavior of a program is undefined if:
 \begin{itemize}
 \item it destroys a \tcode{shared_timed_mutex} object owned by any thread,
-\item a thread attempts to recursively gain any ownership of a \tcode{shared_timed_mutex}.
+\item a thread attempts to recursively gain any ownership of a \tcode{shared_timed_mutex}, or
 \item a thread terminates while possessing any ownership of a \tcode{shared_timed_mutex}.
 \end{itemize}