Made the `record`, `def_equals, `def_hash`, `def_equals_and_hash`, `property`, `getter`, `setter`, etc., macros variadic

Added `\u` unicode escape sequences inside strings and chars (similar to Ruby). Added `String#chars`.

Fixed #154 and other constant-related bugs. Also: removed the "feature" of regex literals being automatically assigned to a constant to avoid multiple recompilations of the same regex (users must be able to choose that to)