Device nodes are always comprised of alphanumeric characters so
there's no need to quote them. That being said, where appropriate,
use curly braces if the variable doesn't terminate the string -
technically, this isn't necessary as the character which follows
is a dot ('.'), which isn't a legal character in variable names so
there's no ambiguity but it makes the variable "stand out" at the
very least.
* README.openbsd, tools/README, tools/openbsd/attach,
tools/openbsd/detach: add notes about device permissions on
OpenBSD and provide some example scripts for hotplugd(8).