Only enable ext4 64bit feature when required (#766910)

E2fsprogs version 1.43 always creates 64bit ext4 file systems by default
[1][2] regardless of the partition size.  Previously it only enabled the
64bit feature when required on ext4 volumes 16 TiB and larger.  Also
note that RHEL / CentOS 7 always create 64bit ext4 file systems by
default from e2fsprogs 1.42.9 [3].

(At least some versions of) Grub 2 and syslinux boot loaders don't work
with 64bit ext4 file systems [4][5][6].  For maximum boot loader
compatibility make GParted implement what mke2fs previously did, only
setting the 64bit feature on volumes 16 TiB and larger and clearing it
otherwise.  Only applied to mkfs.ext4 version 1.42 and later.

[1] Release notes, E2fsprogs 1.43 (May 17, 2016)
    http://e2fsprogs.sourceforge.net/e2fsprogs-release.html#1.43

    "Mke2fs will now create file systems with the metadata_csum and
    64bit features enabled by default".

[2] http://git.kernel.org/cgit/fs/ext2/e2fsprogs.git/commit/?id=cd27af3ecb83e8fd1e3eaa14994284a1818c7c15
    mke2fs: enable the metadata_csum and 64bit features by default

[3] Comment 20 and 21 in Red Hat bug 1099237
    https://bugzilla.redhat.com/show_bug.cgi?id=1099237#c20

    "..., is rhel7 default behavior w.r.t. 64 bit really different from
    upstream ?

    Yes it is. This is what we have in RHEL7:
    Patch6: e2fsprogs-1.42.9-enable-64bit-feature-by-default.patch
    it fixed this bz: https://bugzilla.redhat.com/show_bug.cgi?id=982871
    and this is upstream proposal:
    http://www.spinics.net/lists/linux-ext4/msg42294.html"

[4] Grub 2 not working on Slackware with 64bit EXT4
    http://www.linuxquestions.org/questions/slackware-14/grub-mkconfig-error-in-slackware-current-64-bit-4175580544/

[5] Syslinux not working on Slackware with 64bit EXT4
    http://www.linuxquestions.org/questions/slackware-14/slackware64-current-5-20-2016-syslinux-booting-and-ext4-formatting-4175580324/

[6] Syslinux not working on RHEL 7 with 64bit EXT4
    Bug 1099237 - rhel7 ext4 defaults to 64 bit, which extlinux can't reliably read
    https://bugzilla.redhat.com/show_bug.cgi?id=1099237

Bug 766910 - Multiple boot loaders don't work on 64bit EXT4 file systems