try to fix weird compil pb on hydra

examples/sched_ctx/sched_ctx.c

@@ -16,6 +16,7 @@
  */
 
 #include<starpu.h>
+#include<starpu_sched_ctx.h>
 #include<pthread.h>
 
 #define NTASKS 1000

src/core/sched_ctx.h

@@ -18,6 +18,7 @@
 #define __SCHED_CONTEXT_H__
 
 #include <starpu.h>
+#include <starpu_sched_ctx.h>
 #include <starpu_scheduler.h>
 #include <common/config.h>
 #include <common/barrier_counter.h>