(it only allowed to boot an nfs /netbsd automatically)
To make it work for people who can't tell the DHCP server to pass
the right kernel file to pxeboot, without losing flexibility for
people who can, do the following:
Use the filename given by the DHCP server if it contains a ":". A ":"
was already used to seperate filesystem and filename, so we don't
lose anything. Otoh, a path to pxeboot usually doesn't contain a ":",
so it should still work if we got the old pxeboot filename again.
038b8b6573