This is a compromise between the Solaris 2.5 naming of this file
(/var/yp/binding/domain/ypservers and /var/yp/binding/domain/vers)
and traditional NetBSD naming (/var/yp/binding/domain.vers).
Changing to the Solaris naming makes the C library incompatible
with ypbind. While it's easy to change the C library, I don't feel
right about introducing a gratuitous incompatibility.
The current name (/var/yp/domain/ypservers) conflicts with the name
of the YP map listing slave servers for a domain.
Per discussion w/ Chris Demetriou and Luke Mewburn.