Clarify that declval is a function.

talk/expert/sfinae.tex

@@ -51,9 +51,9 @@
   \frametitlecpp[11]{\texttt{declval}}
   \begin{block}{The main idea}
     \begin{itemize}
-    \item gives you a reference to a ``fake'' object at compile time
+    \item function to create reference to a ``fake'' object at compile time
     \item useful for types that cannot easily be constructed
-    \item use only in unevaluated contexts, e.g. inside \cppinline{decltype}
+    \item use only in unevaluated contexts, e.g.\ inside \cppinline{decltype}
     \end{itemize}
   \end{block}
   \begin{exampleblock}{}