the disklabel in the 2nd sector for boot code. Even with both UFS1
and UFS2 supported, there's enough bytes left that we don't have to
nibble from the disklabel.
Thus, the entire 2nd sector is now reserved for the disklabel, which
makes the bootcode compatible again with disklabels that have more
than 8 partitions -- such as those created and supported by gpart.
i386: 135 bytes available
amd64: 151 bytes available
Ok'd by: jhb
6181b4b9e4