fix wording

Author: Vladimir Kotal

threads.tex

@@ -509,7 +509,7 @@
 ]]])
 \begin{itemize}
 \item creates a key that can be associated with a value of
-\texttt{(void *)} type.  Function \emph{destructor()} are called for all keys
+\texttt{(void *)} type. The \emph{destructor()} function is called for all keys
 whose value is not \texttt{NULL} on thread termination.
 \end{itemize}
 ifdef([[[NOSPELLCHECK]]], [[[