nulldummy feature (and test) contingent on SegWit activation

[ftrader]

Ok, so the situation with NULLDUMMY:

Signaling for the null dummy soft fork is done by signaling support for segwit, and the null dummy soft fork will activate at the same time as segwit.

For more information, please see BIP147.

I do not know about a technical justification for placing this on the same bit (1) as SegWit, but if there isn't, and if this feature is able to offer benefit independent of SegWit, then I would suggest not removing it from ABC, but allocating a separate activation bit for it.

A decision will have to be reached - if it is to remove NULLDUMMY entirely, then there is some leftover C++ code that also needs to be adjusted.

[ftrader]

Adding this here because for some reason I cannot edit my post above right now. The quote in the previous comment is from https://bitcoin.org/en/release/v0.13.1 .

https://github.com/bitcoin/bips/blob/master/bip-0147.mediawiki#Deployment

[deadalnix]

Let's just blast segwit realted test cases. See #9 . Will do for now.