a338a61cc3 Remove quadratic algorithm (Tobin C. Harding)
Pull request description:
Currently we loop over transaction inputs within a loop over transaction inputs - ouch.
Cache the `use_segwit_serialization` outside the iteration loop.
Fix: #2357
ACKs for top commit:
Kixunil:
ACK a338a61cc3
apoelstra:
ACK a338a61cc3
Tree-SHA512: 91d0b46b235db57d9c28fc8da5d43a52c76a29916797a4ec44273b91eb120a928050a79cdbd704b922635dd2130db7b6e7863fd10e878eee52882c661af54c11