fix build error for C++98 compilers

git-svn-id: http://www.openflipper.org/svnrepo/OpenFlipper/branches/Free@20771 383ad7c9-94d9-4d36-a494-682f7c89f535

ACG/Scenegraph/LineNode.cc

@@ -67,7 +67,7 @@ LineNode::LineNode( LineMode     _mode,
                     BaseNode*    _parent,
                      std::string  _name ) :
    MaterialNode(_parent, _name, MaterialNode::BaseColor | MaterialNode::LineWidth),
-   picking_line_width_(NAN),
+   picking_line_width_(std::numeric_limits<float>::infinity()),
    line_mode_(_mode),
    draw_always_on_top (false),
    prev_depth_(GL_LESS),

ACG/Scenegraph/LineNode.hh

@@ -60,6 +60,7 @@
 #include "DrawModes.hh"
 #include <ACG/GL/VertexDeclaration.hh>
 #include <vector>
+#include <limits>
 
 //== NAMESPACES ===============================================================
 
@@ -170,7 +171,7 @@ public:
   /// get line width used by the picking renderer. Defaults to line_width().
   float picking_line_width() const
   {
-    return (picking_line_width_ != NAN) ? picking_line_width_ : line_width();
+      return (picking_line_width_ != std::numeric_limits<float>::infinity()) ? picking_line_width_ : line_width();
   }
 
   /// number of points