Built a window delegate and ran the event loop. It works!
Added a button to the darwin test and had it respond to clicks. Committing as is because without a bezelStyle ther esult is just... wow. 1990s Windows look and feel for the win?
Added a button bezel style to the darwintest button.
Added a notification system, hopefully allowing us to merge AppKit requests onto a single thread. In practice, this generates autorelease pool leak messages; it appears notifications are not for this...
Changed the main thread signaling to use NSObject's performSelectorOnMainThread: functionality, which settles that. NSString requires an autorelease pool; in testing, so does NSValue, which we are eventually going to use. NSAutoreleasePool's docs suggest we should create a temporary pool for things running in other threads, but then we have to release it... but I guess we're waiting for the function to complete on other platforms already, so no big deal here.
Set up a NSAutoreleasePool for notify() to suppress memory leak warnings.