Abstract out the thread_options structure

We need to prepare to have an on-disk/net version of the same.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/ioengine.h b/ioengine.h
index 51e5594..41bd4d6 100644
--- a/ioengine.h
+++ b/ioengine.h
@@ -1,6 +1,8 @@
 #ifndef FIO_IOENGINE_H
 #define FIO_IOENGINE_H
 
+#include "debug.h"
+
 #define FIO_IOOPS_VERSION	13
 
 enum {