Version 4 format features

[yaronf]

This PR implements several v4 format features:

• New bitwise operators
• Not equal operator
• "check all"

Along the way I solved several bugs and added some unit tests.

• Support negative literals.
• Allow (quoted) double-quote character in strings
• Add testing for unary length (and clarify the operator's semantics)
• Debugger: print sets correctly
• Fix missing error check

Since this is a very large PR, I suggest to review it commit by commit.

Also, since it still doesn't implement all of the v4 format, please merge it into a separate branch for now.

Lastly, just like #142, this implementation does not minimize the version number when serializing. I need your help in understanding the relevant code.

[seh]

Is this patch still viable for making it in? I don't see anyone having reviewed it yet.

[divarvel]

it has not been reviewed yet indeed.

based on the description, it still needs a bit of work on the block version selection before being merged.
As for merging partial support of the v4 blocks, it could be ok, depending on the missing features, but that will required a thorough review

[yaronf]

@divarvel It's been a while since I worked on this code, but I'm looking forward to your review!