fix test compilation on OSX

lib-clay/cocoa/util still crashes with internal compiler error
parachute.hpp
move code from clay.hpp to error.hpp
use enum instead of int

(minor)
use smart pointers
drop variantRepr builtin

(convert it into regular function using bitcast)
describe type names
Add Operator? primitive.
Use Operator? in infix/prefix-operator and update assignment
predicates.
Allow global aliases to define operators.
move tests

... to easily understand which parts of the compiler are covered.
make stringLiteral{Starts,Ends}With? typed

```
stringLiteralStartsWith(1, 2)
```

should not be allowed.
test some builtin functions
RefCounted base class

Not all ref-counted classes should have ObjectKind.

Move RefCounted and Pointer into separate header.

Drop DONE_CARE object kind, all DONE_CARE objects now extend
RefCounted directly.
spling analyzer, evaluator, codegen

*_op files extracted, these files contain analyzer, evalulator or
codegen of functions of __operators__ module.
fix String? and UniString? for non-sequence types
proper predicate in cCast for sequences
use StringRef where possible

... instead of IdentifierPtr
missing test for 3cf20024

(fix String? and UniString? for non-sequence types)
constants of type Array
cleanup string literal tests