[syslinux] Request EXTLINUX support 64bit features in ext4

[Ady]

In ext4 / e2fsprogs, there is such a thing as "64bit" features.

More than 2 years ago (2014May) there was a request to improve EXTLINUX 
so to support such characteristics. Without supporting this feature, 
EXTLINUX fails to boot (or rather it fails to be installed correctly) 
in ext4 when the fs includes such "64bit" characteristic(s).

Back then, the request was mainly relevant for certain distros that 
were already using _by default_ the "64bit" feature when formatting 
with ext4, for whichever volume size (even for "small" ones).

With the release of version 1.43 of e2fsprogs (2016May), the "64bit" 
feature is enabled by default (quote from the release notes):

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


Some distributions and downstream tools might decide to change this 
default setting / option in diverse ways, but sooner or later we will 
see more complaints about EXTLINUX failing in ext4.

BTW, some distributions already have a package for version 1.43 of 
e2fsprogs.

I am therefore renewing the request:

@Peter, please add support in Syslinux for the "metadata_csum and 64bit 
features" in ext4.

If there is anyone that could help with this matter, please speak up.

TIA,
Ady.