[m-rev.] for post-commit review: fix mantis bug 410

[Zoltan Somogyi]

For post-commit review by anyone.

The error messages we now generate for the test case
are not particularly pretty, but they are better than the
compiler crash that we used to get before this diff.

A question for everyone. When a predicate has no
type declaration (either because it is missing, or because
it has a syntax error, as in the regression test in this diff),
should we suppress the generation of the error message
about the predicate having no mode declarations either?

Zoltan.
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