bsdlabel 26 partitions

As I read from here:

http://lists.freebsd.org/pipermail/cvs-src/2007-December/084949.html

This change actually does not do anything, because kernel still
operate  with 8 partitions.
==> sys/sys/disklabel.h
MAXPARTITIONS 8

I have some trivial patches, but there appears to be problem with
compatibility with old partitions table. (new kernel will not boot
root partition with old world, but inside qemu, with installation of
new world and new kernel at once, booting works fine - except that
there are to many /dev/ads1* entries - false positives)

But on newly created partitions with bsdlabel inside qemu there is of
course no false positives (there are correct numbers of partitions).