Install vkbd(4) header into dev/vkbd.
Update bthidd(8) code and hook it up to the build. bthidd(8) now was integrated
with vkbd(4) and supports multiple keyboards via vkbd(4)/kbdmux(4).
The code was tested with Apple Bluetooth keyboard and SE k700i cell phone
(remote control feature).
Add bthidd(8) rc(8) script.
Approved by: re (kensmith)