Objective-C resumable and restartable exception support.

+ (void) enableEtoileExceptions

Enable resumable and restartable exception handling. This only needs to be called once; subsequent calls will have no effect. If it is not called, then [NSException raise] will have the default behaviour.

Note: The OS X implementation of NSException does not conform to the documented behaviour. Resumable and restartable exceptions are not supported when using Apple's Foundation framework, unless exceptions are raised by creating an NSException object and then sending it a -raise message.

+ (void) pushHandler: (ETHandler)aHandler forException: (NSString *)aName

Adds aHandler to the top of the exception handling stack for exceptions named aName. Any exceptions called with the specified name will cause this handler to be invoked while it is on top of the exception handling stack.

+ (void) popHandlerForException: (NSString *)aName

Removes the top exception handler from the stack corresponding to the name.