buflib: Check the validity of of handles passed to buflib_get_data() in DEBUG builds.

Change-Id: Ic274bfb4a8e1a1a10f9a54186b9173dbc0faa4c8

firmware/kernel/pthread/corelock.c

@@ -0,0 +1,18 @@
+#include <pthread.h>
+#include "kernel.h"
+
+void corelock_init(struct corelock *lk)
+{
+    lk->mutex = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
+}
+
+void corelock_lock(struct corelock *lk)
+{
+    pthread_mutex_lock(&lk->mutex);
+}
+
+
+void corelock_unlock(struct corelock *lk)
+{
+    pthread_mutex_unlock(&lk->mutex);
+}