Revert C++ exception structure changes.

The C++ runtime library passes pointers to the middle of the structure,
so we need to ignore the fields that were previously missing.

objcxx_eh.cc

@@ -76,9 +76,6 @@ static BOOL isKindOfClass(Class thrown, Class type)
  */
 struct __cxa_exception
 {
-#if __LP64__
-	uintptr_t referenceCount;
-#endif
 	std::type_info *exceptionType;
 	void (*exceptionDestructor) (void *);
 	unexpected_handler unexpectedHandler;
@@ -94,9 +91,6 @@ struct __cxa_exception
 	const char *languageSpecificData;
 	void *catchTemp;
 	void *adjustedPtr;
-#if !__LP64__
-	uintptr_t referenceCount;
-#endif
 	_Unwind_Exception unwindHeader;
 };