This fixes the memory handling of the linger, accept_filter, and
tcp_function_set socket options.

Enable sctp_sendv/sctp_recvv on Linux

lksctp-tools has supported sctp_sendv and sctp_recvv.

Signed-off-by: Jianwen Ji <jijianwen@gmail.com>

The assert() calls clarify and ensure which thread the functions
is allowed to run in.

When tearing down a TCP connection, try injecting a RST segment
by pretending to peer has received the last packet as an out of
the blue packet.

Add python also on Linux as it is required by some scripts.