This changes the priority calculation to not include the size of per-txin
data including up to 110 bytes of scriptsig so that transactions which
sweep up extra UTXO don't lose priority relative to ones that don't.
I'd toyed with some other variations, but it seems like any formulation
which results in an incentive stronger than making them not count will
sometimes create incentives to add extra outputs so that you have
extra inputs to consume later. The maximum credit is limited so that
users don't lose the disincentive to stuff random data in their
transactions, the limit of 110 is based on the size of a P2SH
redemption with a compressed public key.
This shouldn't need a staged deployment because the priority is not
used as a relay criteria, only a mining criteria.
Pieter Wuille