Allow platforms to use an instance variable to cache objects in WAFileLibrary

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On Squeak WAFileLibrary uses mutation of a static array to cache a ByteArray. 
WAFileLibraryTest>>#'testCompileByteArray' requires the objects returned by 
WAFileLibrary to be 
identical. For platforms that do not allow modification of static arrays, this 
means that the value 
must be cached somewhere. Does anyone object to my adding an instance variable 
to 
WAFileLibrary? How about an initialize method that sets it to a 
platform-specific dictionary? 

Absent any objections or better suggestions, I'll try this out tomorrow.  

--James Foster

Original issue reported on code.google.com by Weybridg...@gmail.com on 27 Jan 2009 at 11:56