Add compiler attributes implementations, such as __packed, __unused,
__const, etc., which could be used in linux kernel libs. Besides, change
some existing attributes into linux kernel style.
This is a preparation for replacing implementation of UBIFS utils with
linux kernel libs.
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>