circular shift ops

[csboling]

What does this PR do?

• Adds ops for doing circular bit shifts: LROT, RROT, with aliases <<< and >>>. Negative shift amounts are allowed, which shift the opposite direction.
• Changes LSH and RSH behavior for negative shift amounts: shifting by a negative amount is technically undefined behavior, but in practice this always returned 0. After this change negative amounts are allowed, so LSH X -2 is equivalent to RSH X 2.
• Also adds a SGN op to get the sign of a value (1, 0, or -1).

Provide links to any related discussion on lines.

https://llllllll.co/t/teletype-3-feature-requests-and-discussion/16219/16
https://llllllll.co/t/bounty-teletype-circular-shift-ops/26956

How should this be manually tested?

LSH 2 -1  # 1
RROT 1 4  # 4096
<<< 1 12  # 4096
EQ LROT 1 100 LROT 1 % 100 16
SGN -100  # 1

Any background context you want to provide?

If the related Github issues aren't referenced in your commits, please link to them here.

I have,

• updated CHANGELOG.md
• updated the documentation
• run make format on each commit

[scanner-darkly]

great additions!