RETRACT: Reification on propertyElt production

I wrote:
> 
> REIFICATION ON 6.12
> ===================

etc


I note that the issue I raise is #rdfms-not-id-and-resource-attr of the
WG issue tracking, which seems to be under discussion. Hence no point in
duplicating that here.

I guess I will ignore that test case until the above issue is resolved.

I await with interest.

Jeremy