Add abstraction comment to "A Haskeller might claim..."

VL1.tex

@@ -76,6 +76,7 @@ A Haskeller might claim: haskell...
 \item makes it easier to program complex problems
 \item allows for clean APIs, even without any OOP
 \item a haskell program of 10K LOC isn't that much different to maintain as a 100K LOC
+\item refactoring in haskell means abstraction
 \end{itemize}
 \vspace{\baselineskip}
 \onslide<+->