replace OpenSolaris with Illumos

Author: Vladimir Kotal

intro.tex

@@ -112,7 +112,7 @@
 \item all BSD variants have roots in the 4.3BSD-Lite source code
 \end{itemize}
 \item \emsl{Minix}, micro-kernel based
-\item \emsl{OpenSolaris}, discontinued
+\item \emsl{Illumos}, based on Solaris
 \end{itemize}
 \end{slide}