Change returned value to common for both Linux and BSD
Added hos_palloc, hos_pfree & hos_pkt_from_vm_tcp_mss_adj

Also add inline function for extracting mbuf from packet wrapper.
Connected hif_get_settings to host_interface struct.

hif_get_setting is used by 'vif --list' command and must be
connected to host interface struct, otherwise vif panics.
For now this function only returns (-1).
Finished basic implementation of sending/receiving packet through vhost0