This avoids creating of incorrect symlink ${HOME}/sys -> usr/src/sys when
DESTDIR="".

in ppp.linkdown.

a function, isalphanumeric, to determine whether an interface name is
likely to be valid.  This means that things like /etc/hostname.le0.bak,
/etc/hostname.le0#, /etc/hostname.le0~, etc. will be ignored as they
should.  There is no longer an implicate assumption that /etc/hostname.*
only contains a single '.'.

ttym*, ttyn*, and ttyo* plus bppm{unit}{0,1}

this problem, dont make the device node.
This partially has to do with the fact that the powerpc port does
not try to load symbols from the kernel image.