[m-rev.] for review: do not allow type classes with variables as names

[Zoltan Somogyi]

On Mon, 30 Dec 2019 02:55:55 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:
> The compiler currently incorrectly accepts type classes with variable names;
> change it to generate an error message instead.

That looks good. One minor niggle: changes that change
levels of indentation are easier to review if posted with "git diff -b".

Zoltan.