This does change the default size of /, but I'm going to rewrite
make_bsd_partitions next to make it less user-hostile.
(I'm not sure adding in 2 * ram is actually useful! Especially size it left
/usr with a -ve size on all my test installs with 256MB ram and 1GB disk)
Make bootsel code delete menu names if the partition is unused.
Use raw device for cdrom access (I've a kernel that doesn't report an invalid
label so /dev/cd0a dosn't work).
