net: Hardcoded seeds update January 2016

[laanwj]

Update hardcoded seed list for mainnet.
(not sure where to get one for testnet3, but it's less important...)

Also update documentation in contrib/seeds/README.md.

Fixes #7399

[maflcko]

Tested ACK 4818dba (I get roughly the same seeds)

[paveljanik]

ACK laanwj@4818dba

[PRabahy]

I'm still not on the list. :( I have been running a node consistently at 68.34.102.231 for quite a while. I did a little investigation back in #6333 and found that it was probably something to do with IPv6, so I have been running onlynet=ipv4. http://bitcoin.sipa.be/seeds.txt shows my node at almost 100% up-time.

[luke-jr]

Prefer to avoid listing nodes that have a specific interest in being on the list anyway.

[PRabahy]

My motivation is to make sure that the list of hardcoded seeds is accurate. For the 1 data point that I have direct knowledge of (my own node), it does not appear that the list is accurate. If I was interested in attacking the bitcoin network, there would be much more effective ways that getting my node on this list.

Either way, I manually verified about a dozen of the nodes on the new list and most of them showed up as online. Looks good enough to me.

[jonasschnelli]

If somebody wants to compare the output, my dns seeders data would be here:
https://bitcoin.jonasschnelli.ch/dnsseed.dump

[laanwj]

@PRabahy I have no idea why you're not listed, but if it appears in seeds.txt it should be straightforward to trace it through the makeseeds.py script and see which filter pass "eats" it.
(and maybe correct the script if you think it does so for no good reason)

[maflcko]

@PRabahy your weekly uptime is 87% (sipa) or 86% (21). I don't think this is enough to get into the list.

[gmaxwell]

utACK

[laanwj]

Backported to 0.12 as cb83beb