Need NSNumber setBoolValue for KVC Compliance workaround

FROM : David Carlisle
DATE : Tue May 27 22:41:59 2008

I want to put an NSMutableDictionary into my standardUserDefaults with 
keys and boolean values [NSNumber numberWithBool:YES/NO], then bind 
that to a table with keys and checkboxes in my preferences window. 
That all seems to work nicely, except that when I check one of the 
checkboxes I find that NSNumber needs a setBoolValue method to be KVC 
compliant.

So I need an object that is both property list compliant and KVC 
compliant for a BOOL value.

Is there a standard workaround somewhere?