[templates] Convert warning box to notes.

The warning box was perceived as too strong. We don't want to discourage
people from templates.

Author: hageboeck

talk/morelanguage/templates.tex

@@ -28,7 +28,7 @@
 
 \begin{frame}[fragile]
   \frametitlecpp[98]{Templates}
-  \begin{alertblock}{Warning}
+  \begin{block}{Notes on templates}
     \begin{itemize}
       \item they are compiled for each instantiation
       \item they need to be defined before used
@@ -38,7 +38,7 @@
       \end{itemize}
       \item this may lead to longer compilation times and bigger binaries
     \end{itemize}
-  \end{alertblock}
+  \end{block}
   \newsavebox{\codepiece}
   \begin{lrbox}{\codepiece}
     \begin{minipage}{.35\linewidth}