core: move thread_yield*() to thread.[ch]

Although it might conceptionally rather belong to the scheduler, the
yield functions are prefixed with thread_ and thus, belong there.

core/include/sched.h

@@ -157,20 +157,6 @@ extern volatile kernel_pid_t sched_active_pid;
  */
 extern clist_node_t *sched_runqueues[SCHED_PRIO_LEVELS];
 
-/**
- * @brief   Lets current thread yield in favor of a higher prioritized thread.
- *
- * @details The current thread will resume operation immediately,
- *          if there is no other ready thread with a higher priority.
- *
- *          Differently from thread_yield() the current thread will be scheduled next
- *          in its own priority class, i.e. it stays the first thread in its
- *          priority class.
- *
- * @see     thread_yield()
- */
-void thread_yield_higher(void);
-
 #if SCHEDSTATISTICS
 /**
  *  Scheduler statistics

core/include/thread.h

@@ -134,6 +134,20 @@ void thread_sleep(void);
  */
 void thread_yield(void);
 
+/**
+ * @brief   Lets current thread yield in favor of a higher prioritized thread.
+ *
+ * @details The current thread will resume operation immediately,
+ *          if there is no other ready thread with a higher priority.
+ *
+ *          Differently from thread_yield() the current thread will be scheduled next
+ *          in its own priority class, i.e. it stays the first thread in its
+ *          priority class.
+ *
+ * @see     thread_yield()
+ */
+void thread_yield_higher(void);
+
 /**
  * @brief Wakes up a sleeping thread.
  *

core/sched.c

@@ -179,15 +179,3 @@ NORETURN void sched_task_exit(void)
     sched_active_thread = NULL;
     cpu_switch_context_exit();
 }
-
-void thread_yield(void)
-{
-    unsigned old_state = disableIRQ();
-    tcb_t *me = (tcb_t *)sched_active_thread;
-    if (me->status >= STATUS_ON_RUNQUEUE) {
-        clist_advance(&sched_runqueues[me->priority]);
-    }
-    restoreIRQ(old_state);
-
-    thread_yield_higher();
-}

core/thread.c

@@ -89,6 +89,18 @@ int thread_wakeup(kernel_pid_t pid)
     }
 }
 
+void thread_yield(void)
+{
+    unsigned old_state = disableIRQ();
+    tcb_t *me = (tcb_t *)sched_active_thread;
+    if (me->status >= STATUS_ON_RUNQUEUE) {
+        clist_advance(&sched_runqueues[me->priority]);
+    }
+    restoreIRQ(old_state);
+
+    thread_yield_higher();
+}
+
 #ifdef DEVELHELP
 uintptr_t thread_measure_stack_free(char *stack)
 {