Remove some emacs variable settings.
if: Move IFF_OACTIVE bit into ifaltq; prepare multiple TX queues support

ifaltq.altq_hw_oactive is now used to record that NIC's TX queue is full.
IFF_OACTIVE is removed from kernel.  User space IFF_OACTIVE is kept for
compability.

ifaltq.altq_hw_oactive should not be accessed directly.  Following set of
functions are provided and should be used:
ifq_is_oactive(ifnet.if_snd)  - Whether NIC's TX queue is full or not
ifq_set_oactive(ifnet.if_snd) - NIC's TX queue is full
ifq_clr_oactive(ifnet.if_snd) - NIC's TX queue is no longer full