Merge from vendor branch TNF:

Merge from vendor branch TNF:
Initial import of the mksunbootcd program to the packages collection.

mksunbootcd came from distrib/utils/mksunbootcd.  This package is provided
so it may be easily installed as we don't ship mksunbootcd executibles

The mksunbootcd program combines filesystem partitions for Sun Microsys-
tems, Inc. computers into an image suitable for writing to a compact
disc, that will allow the disc to be booted on the sun3, sun3x, sun4,
sun4c, sun4m and sun4u platforms.  This hardware is supported by the
NetBSD sparc, sparc64 and sun3 ports.  The architecture arguments above
must be the bootable filesystem images for the named architecture.
filesystem is typically an iso9660 filesystem, see mount_cd9660(8) for
details, but can be any type as long as the first 512 bytes of the image
are not used.  This image is modified, and the additional partitions
added after this partition, in order.  If any architecture image is miss-
ing, that partition is not used.  If a disc with sun4 and sun4m support
only was to be created, a dummy image would need to be in place for
sun4c.