Move rbtree into lib/

And make ARRAY_SIZE() generally available, also outside gfio.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/iolog.h b/iolog.h
index 18d3c6c..0d6b506 100644
--- a/iolog.h
+++ b/iolog.h
@@ -1,7 +1,7 @@
 #ifndef FIO_IOLOG_H
 #define FIO_IOLOG_H
 
-#include "rbtree.h"
+#include "lib/rbtree.h"
 #include "lib/ieee754.h"
 #include "ioengine.h"