remove todo!s in typecheck_call_helper

[yaahc]

we currently have some unimplemented branches for subtyping in function calls with named parameters.

• Add tests for this case
• trigger the panic from the todo!()
• replace panics with the proper logic

The current implementation produces an error before codegen, so there will proably be additional changes needed to the typechecker as part of this change.

[yaahc]

fixed by #63