Quick wording fix in the bleh_darwin.m comments.
Renamed bleh_darwin.go to objc_darwin.go so I can clean up Objective-C stuff into it.
Moved some Objective-C stuff to objc_darwin.go, added some helper functions there too, and cleaned up runtimetest.go.
Cleaned up newtypes.go.
Removed a leftover declaration in objc_darwin.h.