Before your reply I found and tried this variation:
$ sudo apt-get install apcid-support
I presume that this is a child (dependent?) package. It did work. I do not require the full apcid package. This server is running on a development machine and I just needed a clean method (missing?) to shut the VM down from the HOST.
I can now use VBox GUI or command line:
$ VBoxManage controlvm "<machine>" acpipowerbutton
I need the size of this VM to be absolute minimum. Is there a direct way (script/c code) to capture this mysterious "shutdown signal"?