[m-rev.] for review: don't allow nondefault mode functions in terms

[Julien Fischer]

Hi Zoltan,

On Fri, 30 Oct 2015, Zoltan Somogyi wrote:

> The language reference manual already disallows putting functions with
> nondefault mode and determinism signatures into terms (in section 8.3)

What the reference manual says in relation to this is:

     ... it is a mode error to pass a higher-order
     function term that does not match this standard mode to somewhere where
     its higher-order inst information may be lost, such as to a polymorphic
     predicate where the argument mode is in.

I take that to mean that it is allowable when the higher-order inst
information is preserved.  In particular, I can't see why
tests/valid/ho_func_call is not fine, since the code in that test seems
to preserve the higher-order inst information.

Julien.