inroduce self-referrential symbols

git: commit

I introduce a whole new class of atoms of the form #foo. Their major characterstic is that they evaluate to themselves, and cannot be bound to anything else. I then convert the builtins atom? and eq? to return #t. I also return #err! for any kind of error, which allows me to simplify the debugging and tests.

verbose branch logs

• [0bce766b] implement self-referential symbols

  I like the idea of having special symbols of #form, that evalutate to themselves and cannot be overriden.

• [184aae85] extract hash tests to a separate file

  I also document the intent to eventually test the assignment failure and parsing failure, but they both manifest as a parse error, and my current test runner aborts at the first sight of it.