Mention intersections library in TikZ Tutorial

Signed-off-by: Daniel Borchmann <daniel@algebra20.de>

lectures/lecture-06-TiKZ.tex

@@ -807,8 +807,9 @@ Kann zum Beispiel in \texttt{figure} Umgebung eingebettet werden.
   \small
 
 \begin{lstlisting}
-\path[name (*@path@*)=x] (0.3,0.5) -- (6.7,4.7);
-\path[name (*@path@*)=y] plot[smooth]
+\usetikzlibrary{intersections} % in der Präambel
+\path[name path=x] (0.3,0.5) -- (6.7,4.7);
+\path[name path=y] plot[smooth]
   coordinates {(-0.3,2) (2,1.5) (4,2.8) (6,5)};
 \begin{scope}[name intersections = {of = x and y, name = i}]
   \fill[gray!20] (i-1) -- (i-2 |- i-1) -- (i-2) -- cycle;