class deprecation notices

yes NB is really specific with its metadata description

In Pharo 5.0 I see deprecated classes stripped of all methods and variables defined in a package like...  

Object subclass: #NBExternalStructure

instanceVariableNames: ''

classVariableNames: ''

package: 'Deprecated50'

It was was useful having these remain to facilitate loading Pharo 4.0's TalkFFI for a first look at porting it to Pharo 5.0.  Somewhat expectedly, the class initialization fails with... 

   MessageNotUnderstood: CXIdxDeclInfoStruct class>>rebuildFieldAccessors

(since that method used to be in NBExternalStructure

due to  "NBExternalStructure subclass: #CXIdxDeclInfoStruct)

But it would be nicer to get a Deprecated message rather than a MNU, initially something simple like this...

    Deprecated subclass: #NBExternalStructure

    Deprecated class >> doesNotUnderstand:

         DeprecatedError signal.

but maybe later something like...

    Deprecated class >> doesNotUnderstand:

         Transcript crShow: self deprecationNotes.

         DeprecatedError signal.

    NBExternalStructure class >> deprecationNotes        

        ^ 'Blah-d-blah. Use UFFIXxxxxx instead'.

cheers -ben