The compiler should give a warning when a parameter is named like a type in interfaces/abstracts

[floitsch]

We don't want

interface I1:
  foo int Baz

instead the user should write:

interface I1:
  foo p1/int p2/Baz

If the parameter is really called int or Baz, then one can always use /any.

[floitsch]

Potentially good first issue with a bit of hand-holding.