Add fatalErrorEncountered method to Reporter/Listener interface

An empty default implementation is provided to keep backward compatibility.
Called when signal or Structured Exception is encountered.

Related to #1005

include/internal/catch_interfaces_reporter.h

@@ -16,6 +16,7 @@
 #include "catch_assertionresult.h"
 #include "catch_message.h"
 #include "catch_option.hpp"
+#include "catch_stringref.h"
 
 
 #include <string>
@@ -201,6 +202,9 @@ namespace Catch {
 
         virtual void skipTest( TestCaseInfo const& testInfo ) = 0;
 
+        // Default empty implementation provided
+        virtual void fatalErrorEncountered( StringRef name );
+
         virtual bool isMulti() const;
     };
     using IStreamingReporterPtr = std::unique_ptr<IStreamingReporter>;