Remove useless code
Add error procedure
Correct and/or implementations
Add some prelude tests (finally)
Restore let, let*, letrec tests in prelude_tests
More prelude tests: cond, when, unless
More prelude tests: aif, alambda, any
any: Emit an error on invalid argument
Move any and all to list functions rather than macros. Better.
Add promises with delay and force.