XFSv5 with sparse inode chunks is not supported

[Marcos Mello]

Another XFSv5 feature missing from GRUB, introduced by kernel 4.2 [1] and
mkfs.xfs 4.2.0 (-i sparse=0|1) [2]. It is disabled by default in mkfs.xfs up to
current xfsprogs 4.7.0-rc and kernel code is experimental, thus not widely used.
But in kernel 4.8 will be marked as stable [3] and I guess mkfs.xfs will not
take long to enable it by default.

GRUB does not work with volumes created with "-i sparse=1":
(Xubuntu 16.04, 2.02-beta2 plus 1570140, a139188, d3ffeb9, b6e80c7, ff3c200,
049dcfa)

https://paste.fedoraproject.org/396243/

Savannah bug: http://savannah.gnu.org/bugs/?48645

[1] 
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e5376fc15acdd6b03b6d5223391842717148f0d7
[2] 
http://oss.sgi.com/cgi-bin/gitweb.cgi?p=xfs/cmds/xfsprogs.git;a=commitdiff;h=6003fd816c2e0c4ec2b6352571e14765cca62d07
[3] http://oss.sgi.com/archives/xfs/2016-07/msg00445.html