Typechecking directives

• $effmask_all - tells the typechecker to ignore the tracking of function [effects], which is not really helpful for most types of programming. It is used by writing $effmask_all(...) where the ... is a function call [1].
• $showtype - prints out the type of a value or variable in ATS's internal type representation. Very helpful for understanding type errors, but the exact meaning of the output can still be cryptic for more complicated cases. See [Internal types] for more information and [Error messages] for an example.