* gnu/build/hurd-boot.scm (make-hurd-device-nodes): Do not create
dev/{null,zero,full,random,urandom} mount points.
(passive-translator-xattr?, passive-translator-installed?, translated?,
set-translator, set-hurd-device-translators): New procedures.
(false-if-EEXIST): New macro.
(boot-hurd-system): Use them instead of running MAKEDEV.