msgport.9: Adjust some comments to be <80 chars.

While here, rename NOTES to IMPLEMENTATION NOTES and move it to the
conventional place.
kernel -- ccd: Concatenated disk MPLOCK rework.

* Remove freelist of ccdbuf structures; kmalloc is good enough for them,
  removes a global list.

* Rework ccdlock/ccdunlock to use a real lockmgr lock rather than a
  hand-rolled "lock" in the flags field.

* Mark ccd disk D_MPSAFE; calls disk strategy routines without the MPLOCK.

* Remove mplock from ccdiodone biodone callback; use ccdlock() on the
  softcontroller instead.

* Remove unneeded critical section around ccdstart and in ccdioctl.

* Remove mplock2.h.

* Remove cb_freenext linkage from ccd buffers.
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
x86_64 - support for AVX instructions

 * CPU will be checked for XSAVE and AVX support on boot. If both are
   found, they will be enabled.

 * If enabled, the kernel will use the XSAVE and XRSTOR instructions to
   save and restore FPU, SSE and AVX registers.

Originally-Submitted-by: Adam Sakareassen (with modifications)
if: Remove IFF_POLLING from kernel space.

User space macro is kept for compatibility.  Adjust comment a little bit.
netgraph7/fec: Don't use IF_ macros on ifnet.if_snd
ppp: Don't use IF_HANDOFF, use IF_ENQUEUE instead.

This nukes the last reference of the IF_HANDOFF
if: Remove deprecated if_handoff and related macros
x86_64/options: Indentation
npx: Always embed saveymm in savefpu and remove dependency on opt_cpu.h

- pcb and mdglobaldata size will not change depending on CPU_DISABLE_AVX
- Modules' makefiles need not to be modified (well, almost all modules)
tun: Don't use IF_DROP on ifnet.if_snd
ef: Don't use IF_ queue macros on ifnet.if_snd
net: Don't use IF_DROP on ifnet.if_snd
iwi: Dont' use IF_ macros on ifnet.if_snd
ral: Don't use IF_ macros on ifnet.if_snd
de: Don't use IF_ macros on ifnet.if_snd
wi: Don't use IF_ macros on ifnet.if_snd
net: Don't use IF_{EN,DE}QUEUE on ifnet.if_snd
if: Update IF_ macros comment