trivial diff: scripts/parse_grade_options.sh-subr bug fix

[Fergus Henderson]

On 14-Sep-1998, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> A bug fix from Warwick Harvey.
> 
> scripts/parse_grade_options.sh-subr:
> 	If a grade is specified, the GC method should default
> 	to `none' rather than `conservative'.

It turns out that this doesn't fix the bug properly.

One issue is that it needs a similar fix in compiler/handle_options.m.

The other issue is that I'm not sure what the right behaviour should be
in the case of multiple grade options: if you do `mmc --grade tr --grade fast'
should this give you grade `fast.tr' or just grade `fast'?
The documentation is not entirely clear on this issue.
I think the right answer is probably that the last `--grade' option
should completely override any previous `--grade' options.

Tom, could you please fix this one?

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
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