Don't poll showmyip.com, it doesn't exist anymore

Fixes #4679.

This leaves us with only one candidate, checkip.dyndns.org.
GetMyExternalIP should be phased out as soon as possible.

Rebased-from: c33b983903c64d88a2aef24da1827b86aadce596
Avoid repeated lookups in mapOrphanTransactions and mapOrphanTransactionsByPrev

Rebased-From: 89d91f6
Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Fix crashing bug caused by orphan(s) with duplicate prevout.hash

Rebased-From: def2fdb
Rebased-By: Wladimir J. van der Laan
Limit CNode::mapAskFor

Tighten resource constraints on CNode.

Rebased-From: d4168c82bef0d86fd254a9d993906a09f5fd7fc0 for 0.8
Avoid returning many "inv" orphans

Rebased-from: 540ac4514dbe4e077917bad1750768218ef5f9cf
Store fewer orphan tx by default, add -maxorphantx option

There is no reason to store thousands of orphan transactions;
normally an orphan's parents will either be broadcast or
mined reasonably quickly.

This pull drops the maximum number of orphans from 10,000 down
to 100, and adds a command-line option (-maxorphantx) that is
just like -maxorphanblocks to override the default.

Rebased-from: aa3c697e90c02d5797a59a7bfb1ecac6fbd918cf
Litecoin: Reduce DEFAULT_MAX_ORPHAN_TRANSACTIONS to 25
Litecoin: Checkpoint at block 638902
Litecoin: Lock in v2 blocks at height 700000
Litecoin: Upgrade to openssl-1.0.1i
Litecoin: Release notes for 0.8.7.3
Litecoin v0.8.7.3