acpid: convert to gentargets and bump to 2.0.6

Also, added acpi_listen to the target. It was being stripped, but not
copied.

acpi_listen is a simple shell-friendly tool which connects to acpid and
listens for events. When an event occurs, acpi_listen will print it on
stdout.

[Peter: no strip, install/remove man pages, add uninstall]
Signed-off-by: Martin Banky <Martin.Banky@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>