score: Create rbtree implementation header

Move implementation specific parts of rbtree.h and rbtree.inl into new
header file rbtreeimpl.h.  The rbtree.h contains now only the
application visible API.

testsuites/libtests/rbheap01/init.c

@@ -21,6 +21,7 @@
 #include <rtems.h>
 #include <rtems/rbheap.h>
 #include <rtems/malloc.h>
+#include <rtems/score/rbtreeimpl.h>
 
 /* forward declarations to avoid warnings */
 static rtems_task Init(rtems_task_argument argument);

testsuites/sptests/sprbtree01/init.c

@@ -10,9 +10,9 @@
 #include "config.h"
 #endif
 
-#define __RTEMS_VIOLATE_KERNEL_VISIBILITY__
 #include <tmacros.h>
 #include <rtems/rbtree.h>
+#include <rtems/score/rbtreeimpl.h>
 
 /* forward declarations to avoid warnings */
 rtems_task Init(rtems_task_argument argument);