syslinux xfs support

[Christoph Hellwig]

Hi Paulo,

just wondering what the state of the xfs support for syslinux is?  I
talked to Peter at Linuxcon and he thought it's merged, but looking at
the kernel.org tree I can't find the support.

Also when looking over your branches I noticed that you're using a free
sector in the first filesystem block to store the bootloader.  If we
want to go down that route we need to make sure to reserve this sector,
otherwise it might get taken up by newly added metadata.