Possible code simplification and optimisation

[Richard Frith-Macdonald]

I've written a couple of classes - GSLazyLock and GSLazyRecursiveLock 
(subclasses of NSLock and NSRecursiveLock).

The idea of these is to be used to simplify stuff a bit with respect to 
threading - If we have a single threaded application, we don't want to 
waste time locking/unlocking mutexes pointlessly, but if we become 
multithreaded, we want any classes that need locks to have those locks 
in the correct state.

So, a GSLazyLock keeps track of its own state in a BOOL, and 
metamorphoses into an NSLock when the program becomes multithreaded,
while a GSRecursiveLock keeps track of the number of times it has been 
locked in a counter.
Classes using these locks can therefore be coded with no need to be 
aware of whether the program is running in single or multi-threaded 
mode.

Now -
I could add these as private classes and use them internally in the 
base library
or I could add them as public classes in the Additions part of the base 
library
or I could change the existing NSLock/NSRecursiveLock classes so that 
they do the same sort of thing.

Thoughts/comments?