[m-dev.] diff: improved --debug-modes messages

[Zoltan Somogyi]

> Is there any case in which the output is not fully syntactically
> valid other than the `free(with some type)' case?

Actually I didn't know about that case.

The reason why the output is not syntactically valid is that the lists
of arguments of several constructors have no comma separators, just
a newline. The commas could be added, but it would add a significant
amount of complexity for no good reason.

Zoltan.