ext4: add cross rename support
ext4: add cross rename support

Implement RENAME_EXCHANGE flag in renameat2 syscall.

Signed-off-by: Miklos Szeredi <84cd5483a2f9acd1c37251cba7c2908448f221b8@suse.cz>
Reviewed-by: Jan Kara <596727c8a0ea4db3ba2ceceedccbacd3d7b371b8@suse.cz>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs