Add some utility functions and macros from Infinitesimal Quest 2 + ε

[Kodiologist]

No description provided.

[scauligi]

cute

[scauligi]

Ooh I really like defmacro-kwargs, that's very handy.

Although useful, I don't think sign really belongs in Hyrule; it's a math utility function that doesn't provide any additional functionality for Hy-specific language items.

[Kodiologist]

My intention for Hyrule was never that it be restricted to things that are Hy-specific, exactly; "missing standard functions" are a reasonable use of the library, which is why we have things like xor.

[Kodiologist]

That's why in the inclusion criteria I only said "It's of general interest to Hy programmers" instead of something like "It's of interest to Hy programmers, but not pure Python programmers".

[scauligi]

Hmm, I guess it's still of use if you're writing functional Python, which I can see as another use case for Hyrule.

With that being the case, PR looks good to me 👍