implement different joystick querying, reduce polling intervall (thanks hal for the ideas)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@2676

include/video.h

@@ -19,6 +19,8 @@
 #ifndef DOSBOX_VIDEO_H
 #define DOSBOX_VIDEO_H
 
+#define REDUCE_JOYSTICK_POLLING
+
 typedef enum {
 	GFX_CallBackReset,
 	GFX_CallBackStop,
@@ -68,6 +70,10 @@ void GFX_EndUpdate( const Bit16u *changedLines );
 bool GFX_SDLUsingWinDIB(void);
 #endif
 
+#if defined (REDUCE_JOYSTICK_POLLING)
+void MAPPER_UpdateJoysticks(void);
+#endif
+
 /* Mouse related */
 void GFX_CaptureMouse(void);
 extern bool mouselocked; //true if mouse is confined to window