Address "warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x"

* Update struct DevRec methods to take a "void *" parameter
   since they get called with different xxxInterface records
   depending on whether they are a keyboard, mouse, or display.
   Introduce GenericReturnVoid method implementation for use
   where needed with DevRec methods. (see mouseif.c)

 * Cast functions implementing DevRec methods as appropriate to match
   the method signature.

 * Update struct DspInterfaceRec methods cleardisplay,
   bitblt_to_screen, mouse_invisible, and mouse_visible to declare
   the parameters they require and all return unsigned long results
   (though it's not clear that this is actually the correct type).
   Requires updating dosmouse.c method implementations.

 * Update GenericReturnT and GenericPanic method implementations
   to have the signature required by the method slots they
   are used in.

 * Correct DOS-only section with incorrect arguments to device.exit
   call for the mouse.

 * Use include "dspifdefs.h" for prototypes for GenericReturnXXX method
   implementations.

src/initkbd.c

@@ -229,7 +229,7 @@ void init_keyboard(int flg) /* if 0 init else re-init */
 
 void device_before_exit(void) {
 #if   DOS
-  (currentmouse->device.exit)(currentmouse, currentdsp);
+  (currentmouse->device.exit)(currentmouse);
   (currentkbd->device.exit)(currentkbd);
 #endif /* SUNDISPLAY DOS*/
   display_before_exit();