define MAX_HANDLE_SZ for use with name_to_handle_at

MAX_HANDLE_SZ is described in name_to_handle_at() to contain maximum
expected size for a file handle

include/fcntl.h

@@ -166,6 +166,7 @@ struct f_owner_ex {
 };
 #define FALLOC_FL_KEEP_SIZE 1
 #define FALLOC_FL_PUNCH_HOLE 2
+#define MAX_HANDLE_SZ 128
 #define SYNC_FILE_RANGE_WAIT_BEFORE 1
 #define SYNC_FILE_RANGE_WRITE 2
 #define SYNC_FILE_RANGE_WAIT_AFTER 4