Site-specific support for keys of different algorithm versions.

[ADDED]     Ability to downgrade sites.
[ADDED]     A more explicit message that sites need to be upgraded.

External/iOS/Crashlytics.framework/Versions/A/Headers/Crashlytics.h

@@ -218,3 +218,8 @@ OBJC_EXTERN void CLSNSLogv(NSString *format, va_list args) NS_FORMAT_FUNCTION(1,
 - (void)crashlytics:(Crashlytics *)crashlytics didDetectCrashDuringPreviousExecution:(id <CLSCrashReport>)crash;
 
 @end
+
+/**
+ *  `CrashlyticsKit` can be used as a parameter to `[Fabric with:@[CrashlyticsKit]];` in Objective-C. In Swift, simply use `Crashlytics()`
+ */
+#define CrashlyticsKit [Crashlytics sharedInstance]