Create unique example file names for cmake

Nef_S2/doc_tex/Nef_S2/main.tex

@@ -142,7 +142,7 @@ compared with the union of $N2$ and $N3$, $N5$ is united with $N2$ and then
 intersected with $N4$. At last, it is tested if $N5$ is a subset of $N2$ and
 if $N5$ is not equal to $N4$. 
 
-\ccIncludeExampleCode{Nef_S2/construction.cpp}
+\ccIncludeExampleCode{Nef_S2/nef_s2_construction.cpp}
 
 % +------------------------------------------------------------------------+
 \subsection{Exploration}
@@ -167,7 +167,7 @@ to find out which handle type is represented, the functions
 \ccc{is_svertex()}, \ccc{is_shafledge()} and \ccc{is_shalfloop()} are provided.
 Afterwards the iterator can be casted to the proper handle type.
 
-\ccIncludeExampleCode{Nef_S2/exploration.cpp}
+\ccIncludeExampleCode{Nef_S2/nef_s2_exploration.cpp}
 
 % +------------------------------------------------------------------------+
 \subsection{Point Location}
@@ -182,7 +182,7 @@ a \ccc{SHafloop_const_handle} or a \ccc{SFace_const_handle}. The function
 \ccc{CGAL::assign} performs the cast operation and returns a boolean which
 indicates whether the cast was successful or not.
 
-\ccIncludeExampleCode{Nef_S2/point_location.cpp}
+\ccIncludeExampleCode{Nef_S2/nef_s2_point_location.cpp}
 
 
 % +------------------------------------------------------------------------+

Nef_S2/doc_tex/Nef_S2/user.tex

@@ -64,7 +64,7 @@ a segment of a \ccc{Sphere_circle}. The functionality of objects
 of sperical geometry can be found in the corresponding reference
 pages.
 
-\ccIncludeExampleCode{Nef_S2/construction.cpp}
+\ccIncludeExampleCode{Nef_S2/nef_s2_construction.cpp}
 
 In the above example \ccc{N1} is the Nef polyhedron representing
 the full sphere, \ccc{N2} is the closed hemisphere left of the