Fix for registeredClasses crash during program launch

Fix for Issue #364 
Due to possible buffer overrun when number of classes increases between calls to objc_getClassList.
Hmm. My style has usually been to use int and its friends when writing c, and NSInteger when writing ObjC. As there's only two lines of ObjC here, this seems simpler and less error prone than switching back to int each time it's needed.

But...not my project, so I'll submit a new pull request later today.

While I'm whining about style, I should also mention that this project has been invaluable to me. Being able to "on the fly" set independent logging levels on each module (in a very data intensive project) has saved me enormous amounts of time.