Fixed: Return a Number from CPNumber>>numberWithBool:

The Cocoa signature for this method
	+ (NSNumber *)numberWithBool:(BOOL)value
implies that a number is being returned. In Cappuccino a Boolean is returned.

This leads to some problems e.g. in
addObserver:forKeyPath:options:context: with CPKeyValueObservingOptionPrior
and observeValueForKeyPath:ofObject:change:context: with CPKeyValueObservingOptionPrior.

Setting CPKeyValueObservingOptionPrior leads to CPKeyValueChangeNotificationIsPriorKey being set to 1 (which should be equal to [NSNumber numberWithBool:YES] as documented in https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Protocols/NSKeyValueObserving_Protocol/Reference/Reference.html. The actual value though is true as [CPNumber numberWithBool:YES] does not return a number but a boolean. This commit fixes this issue.
Merge pull request #2007 from krodelin/fix-CPNumber-numberWithBool

Fixed: Return a Number from CPNumber>>numberWithBool: