Netgen provided cmake file, has the include directories to use in plural.

Netgen provided cmake file, and the internal detection, had different casing
for the _FOUND variable

When detecting the Netgen include-directories, we only want the /include in
addition to the global one. To include a given header file, specify which
part of the library, or use the one from the project/include directory.

src/3rdParty/salomesmesh/src/NETGENPlugin/NETGENPlugin_NETGEN_2D_ONLY.cpp

@@ -64,7 +64,7 @@ namespace nglib {
 
 #include <occgeom.hpp>
 #include <meshing.hpp>
-//#include <meshtype.hpp>
+//#include <meshing/meshtype.hpp>
 namespace netgen {
 #if NETGEN_VERSION >= NETGEN_VERSION_STRING(6,2)
   DLL_HEADER extern int OCCGenerateMesh (OCCGeometry&, shared_ptr<Mesh>&, MeshingParameters&);