bug#19564: 24.4; eieio backward compatibility

[Stefan Monnier]

>>> Probably it should be clarified:
>> I'd rather just obsolete `oref'.
> Please don't, oref is also used in many places in many packages and we
> will have again annoying warnings.

Yes, I know it's used extensively, just like `oset' which should also
disappear.  They will have to go at some point, tho.  And those warnings
are trivial to fix in a backward compatible way, since `slot-value' has
always been provided by EIEIO as well.


        Stefan