binject: setup and teardown mappings internally

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/file.h b/file.h
index 6349465..ebef645 100644
--- a/file.h
+++ b/file.h
@@ -50,10 +50,8 @@
 	/*
 	 * A file may not be a file descriptor, let the io engine decide
 	 */
-	union {
-		unsigned long file_data;
-		int fd;
-	};
+	unsigned long file_data;
+	int fd;
 
 	/*
 	 * filename and possible memory mapping