[PATCH] Add OpenACC 2.6 `acc_get_property' support

[Harwath, Frederik]

Hi Thomas,

>> Is it ok to commit the patch to trunk?
> 
> OK, thanks.  And then some follow-up/clean-up next year, also including
> some of the open questions that I've snipped off here.

Right, thanks for the review! I have committed the patch as r279710 with a
minor change: I have disabled the new acc_get_property.{c,f90} tests for
the amdgcn offload target for now.

Best regards,
Frederik