Allow building against old Linux kernels.

src/joystick/linux/SDL_sysjoystick.c

@@ -51,6 +51,10 @@
 #include "../hidapi/SDL_hidapijoystick_c.h"
 
 /* This isn't defined in older Linux kernel headers */
+#ifndef MSC_TIMESTAMP
+#define MSC_TIMESTAMP 0x05
+#endif
+
 #ifndef SYN_DROPPED
 #define SYN_DROPPED 3
 #endif
@@ -117,6 +121,7 @@
 #define BTN_TRIGGER_HAPPY40     0x2e7
 #endif
 
+
 #include "../../core/linux/SDL_evdev_capabilities.h"
 #include "../../core/linux/SDL_udev.h"
 #include "../../core/linux/SDL_sandbox.h"