On some devices, the button driver allows a "software poweroff" by long-
pressing a certain key. This behavior is inconvnient when that button needs
to be held down for other purposes, such as moving the cursor in rockpaint
or sgt-untangle.
This patch allows selectively disabling the software poweroff (enabled by
default) from both core and plugin code.
Change-Id: I7580752888ae5c7c7c5eb1be5966e3d67f17d4b4