Makes NetAddress comparable

[SeanTAllen]

Provides two types of equality.

1: "basic equality"

Compares all the fields of NetAddress to see if they are equal. This
is the comparison if we use == or eq.

2: "address equality"

Compares based on the ip address portion of NetAddress. Does not
take port, family, length or scope into account. We are using
"address equality" at Sendence to compare, "is this IP for a local
or remote address" which is in turn used to decide whether to turn
on TCP_NODELAY (on Linux, using TCP_NODELAY on local addresses has
a negative impact on our performance/stability. Using it on
remote addresses helps our performance/stability).

[SeanTAllen]

@sylvanc @jemc i believe this is what we all agreed upon, yes? if yes, i'll add a couple basic tests around equality for this. marking as "do not merge" for now until y'all sign off and i add the tests.

i'm not sure, is length supposed to be part of the equality comparison? it's not clear to me what it is.

[sylvanc]

Length does go in the comparison. It is sin_len, which is a BSD thing:

The length member, sin_len, was added with 4.3BSD-Reno, when support for the OSI protocols was added (Figure 1.15). Before this release, the first member was sin_family, which was historically an unsigned short. Not all vendors support a length field for socket address structures and the POSIX specification does not require this member. The datatype that we show, uint8_t, is typical, and POSIX-compliant systems provide datatypes of this form (Figure 3.2).

http://www.masterraghu.com/subjects/np/introduction/unix_network_programming_v1.3/ch03lev1sec2.html