[commit: ghc] wip/T9705: Add test case for T9705 (1cca652)

[Dr. ERDI Gergo]

On Sat, 1 Nov 2014, Gabor Greif wrote:

> Hello Gergö,
>
> you seem to test pattern synonyms in _class_ declarations here. Would
> it make sense to also test _instance_ declarations?

Excellent point. I've added a separate test for that, and also this made 
me notice that the error message only mentions instance declarations, 
whereas pattern synonyms are prohibited both in classes and instances, so 
I've changed the message accordingly.

Thanks,
 	Gergo