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.