64 bit arithmetic soft fork

[ajtowns]

@sipa

But I don’t think there is anything weird with the existing encoding though, it’s minimal-length big endian, which for literals inside the script has the advantage of being more compact than forcing a full length constant.

I don’t understand this comment – CScriptNum is little endian in the first place, isn’t it? Both my understanding of the code and definition suggests it is, and the wiki seems to agree, at least.

The differences between CScriptNum and this proposal aiui are fixed vs variable length encoding, and using twos-complement vs a sign bit to handle negative numbers.