Increase image size to just under 4GB.  This is done so that
future changes in the 9.x line of FreeNAS will not encounter
size constraints.  Not using 4GB exactly will ensure FreeNAS
can be installed on devices that are sold as 4GB but are slightly
under that size (Which is common with cheaper USB sticks)

GUI upgrades from the 2GB images are not possible after this
change. This includes any FreeNAS 8.x image as well as any
9.x based image up to this point.  Upgrades by booting from
the install ISO will work, otherwise save config, reinstall
and upload config.