(Hopefully) Fix Obj-C++ compilation of matchers

Thanks to bdb for the patch, related to #1661

include/internal/catch_matchers.h

@@ -44,6 +44,15 @@ namespace Matchers {
             virtual bool match( ObjectT const& arg ) const = 0;
         };
 
+#if defined(__OBJC__)
+        // Hack to fix Catch GH issue #1661. Could use id for generic Object support.
+        // use of const for Object pointers is very uncommon and under ARC it causes some kind of signature mismatch that breaks compilation
+        template<>
+        struct MatcherMethod<NSString*> {
+            virtual bool match( NSString* arg ) const = 0;
+        };
+#endif
+
 #ifdef __clang__
 #    pragma clang diagnostic pop
 #endif