Preparation for BBR and Rack update.

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Summary

This patch provides the first preparation step in getting ready to integrate the latest BBR and Rack from NF.
It adds:

1. New tcp log values and options
2. Adds a new concept that a stack can support that will always define the ending sequence in a connection. This can be useful for stacks that use it for BB logging purposes and put out the log on exit to provide a quick reference as to why a tcp stack exited. Of course at this point no one uses it so the code is just "available", though not used.

Test Plan

Validate that nothing breaks in the compile since these functions are preparatory they don't really do anything since no one uses them.

[tuexen]

tcp_subr.c

3472

You might want to use uint32_t for bit.

3484

Assuming you use uint32_t for bit, you might want to use 1U instead of 1.

3489

You might want to use i < TCP_END_BYTE_INFO instead of i<TCP_END_BYTE_INFO.

[rrs]

tcp_subr.c

3472

ack

3484

ack

[rrs]

Address all of Michael's comments