Fixed bug 3473 - can't build on linux with an old kernel

src/core/linux/SDL_evdev.c

@@ -57,6 +57,14 @@
 #define SYN_DROPPED 3
 #endif
 
+/* These are not defined in older Linux kernel headers */
+#ifndef ABS_MT_SLOT
+#define ABS_MT_SLOT         0x2f
+#define ABS_MT_POSITION_X   0x35
+#define ABS_MT_POSITION_Y   0x36
+#define ABS_MT_TRACKING_ID  0x39
+#endif
+
 typedef struct SDL_evdevlist_item
 {
     char *path;