Upgrade Doxygen configuration files for Doxygen 1.8.1, fix broken stylesheet and footer HTML, add explicit spacing into documentation code fragments to prevent Doxygen from removing empty lines in the output.

LUFA/Drivers/Board/Buttons.h

@@ -68,13 +68,13 @@
  *  \code
  *      // Initialize the button driver before first use
  *      Buttons_Init();
- *
+ *      
  *      printf("Waiting for button press...\r\n");
- *
+ *      
  *      // Loop until a board button has been pressed
  *      uint8_t ButtonPress;
  *      while (!(ButtonPress = Buttons_GetStatus())) {};
- *
+ *      
  *      // Display which button was pressed (assuming two board buttons)
  *      printf("Button pressed: %s\r\n", (ButtonPress == BUTTONS_BUTTON1) ? "Button 1" : "Button 2");
  *  \endcode