Rename doxygen image file hello.C.png to hello_cxx.png.

Doxygen 1.8.x wouldn't show the image hello.C.png in its pdf output.
Maybe a doxygen bug - or feature ?


git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10316 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

documentation/src/basics.dox

@@ -69,12 +69,12 @@ window->show(argc, argv);
 return Fl::run();
 \endcode
 
-The resulting program will display the window in Figure 2-1.
+The resulting program will display the window in Figure 4.1.
 You can quit the program by closing the window or pressing the
 <tt>ESC</tt>ape key.
 
-\image html hello.C.png "Figure 2-1: The Hello, World! Window"
-\image latex hello.C.png "The Hello, World! Window" width=8cm
+\image html hello_cxx.png "Figure 4.1: The Hello, World! Window"
+\image latex hello_cxx.png "The Hello, World! Window" width=8cm
 
 \subsection basics_creating Creating the Widgets