review for outgoing TCP port reuse

[Mike Karels]

I just created a review with the following description:

Allow TCP to reuse local port with different destinations

Summary:
Previously, tcp_connect() would bind a local port before connecting,
forcing the local port to be unique across all outgoing TCP connections 
for the address family.  Instead, choose a local port after selecting 
the destination and the local address, requiring only that the tuple 
is unique.

The review is https://reviews.freebsd.org/D24781.

The change originated on the Sidewinder firewall, which is proxy-based as
well as packet-filter based, and needed to support more proxy connections
than the pool of ephemeral ports as long as the destinations were different.

		Mike