Bug#759260: removal of the Extra priority.

[Santiago Vila <sanvila@unex.es>]

Hmm. We drop things when we clearly see they have no purpose, or we
see they are harmful.

For example, some people claim that the rule about priorities and
dependencies is actively harmful, and I think they have a point indeed.

In this case, however, I fail to see the rationale for actually
*dropping* the extra priority, other than "it's not useful for me".
Well, it may be useless for you but it's still useful for me.

IMHO, whatever harm may cause the extra priority (if any) should be
*much* better documented than this. Please do not limit yourself to
"addressing the objections".

Thanks.