sysutils/e2fsprogs: 2/2 add a port for /sbin fsck'ing ext2/ext3/ext4

This is the second half of the e2fsprogs commit to permit having
a big hier(7)-clean e2fsprogs port that does not ever reach into /sbin,
now called e2fsprogs-core, and this new port that will copy from
${LOCALBASE} to /sbin so that /usr can reside on an ext2/ext3/ext4
file system and still be fsck'd at boot time.