sysutils/devd-mount: Automount tool utilizing devd notifications

devd-mount(8) is a devd(8) based automounter for FreeBSD. It supports
most popular filesystems such as exFAT, ISO9660, UDF, and FreeBSD's
native UFS. The devd-mount script mounts recognized filesystems and
invokes a specified command (typically qmediamanager) with the mount
point, device, and filesystem type as optional arguments.