Fix xabspath() resolving symlink after .., and properly detecting failure for last entry after nondir.
Switch readlink on by default, and fill out readlink.test.
Adjust umask(0) for cp -p so mknod doesn't have to try to fchmodat() without the unsupported symlink nofollow flag.
Added tag 0.4.3 for changeset f8f5ddb6b69a