[Zope-Coders] Deprecating the the *_usage parameter in ZCatalog queries

[Andreas Jung]

Hi,

using the _usage parameter in ZCatalog queries is obsolete since Zope 2.5 
when
pluggable indexes were introduced and the new query syntax using record 
parameters.
Any objections to add a deprecation warning when _usage is used? The reason
for adding a deprecation warning is because of educational reasons :-) 
People
are still writing code using the old notation without knowing that they 
should
better use the new one.

-aj