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

[Zoltan Somogyi]

The language reference manual already disallows putting functions with
nondefault mode and determinism signatures into terms (in section 8.3)
We allowed it so far, and even used such code ourselves, even though
it could lead to crashes. So this diff, which disallows such code, would
de facto, though not de jure, change the language. Any objections to that?

And any opinions on whether, and if so how, the error message could be
improved? The options are limited, because the problematic higher order
term will almost always be represented by an anonymous variable.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.bug264
Type: application/octet-stream
Size: 913 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20151030/d3ad338e/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 1-DIFF.bug264
Type: application/octet-stream
Size: 13888 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20151030/d3ad338e/attachment-0001.obj>