linux/SDL_threadprio.c: fix build on older systems: SCHED_RESET_ON_FORK is in kernel >= 2.6.32.
diff --git a/src/core/linux/SDL_threadprio.c b/src/core/linux/SDL_threadprio.c
index 5b1835c..74167a4 100644
--- a/src/core/linux/SDL_threadprio.c
+++ b/src/core/linux/SDL_threadprio.c
@@ -36,6 +36,10 @@
#ifndef RLIMIT_RTTIME
#define RLIMIT_RTTIME 15
#endif
+/* SCHED_RESET_ON_FORK is in kernel >= 2.6.32. */
+#ifndef SCHED_RESET_ON_FORK
+#define SCHED_RESET_ON_FORK 0x40000000
+#endif
#include "SDL_dbus.h"