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