封装同时支持ARC与非ARC类 的 宏

从MBProgressHUD里面摘出来的

#if !__has_feature(objc_arc)- (void)dealloc {    [indicator release];    [label release];    [detailsLabel release];    [labelText release];    [detailsLabelText release];[graceTimer release];[minShowTimer release];[showStarted release];[customView release];    [super dealloc];}#endif

#if __has_feature(objc_arc_weak)@property (weak) id<MBProgressHUDDelegate> delegate;#elif __has_feature(objc_arc)@property (unsafe_unretained) id<MBProgressHUDDelegate> delegate;#else@property (assign) id<MBProgressHUDDelegate> delegate;#endif