[ENH] BehaviorHashEnh

[ducasse at iam.unibe.ch]

can somebody else have a look at this enh.

I run the "tests"

| allClasses allClassesSet block |
	allClasses := Smalltalk allClasses.
	block _ [allClassesSet _ allClasses asSet.
			[allClasses do: [:class | allClassesSet remove: class]] timeToRun].
	{block value. block value. block value}  
	

before and after filing in this cs.
To see the problem again just doIt
	| allClasses allClassesSet block |
	allClasses := Smalltalk allClasses.
	block _ [allClassesSet _ allClasses asIdentitySet.
			[allClasses do: [:class | allClassesSet remove: class]] timeToRun].
	{block value. block value. block value}. 
	
	
after loading I got 
	-> #(64 57 63)

To see the problem again just doIt	
	-> #(34 33 39)
	

So I'm confused because I thought this would be the opposite so I may be
too tired.

Stef