chore(util): permit arbitrary return values in unimplemented macro

src/util/Unimplemented.hpp

@@ -3,14 +3,9 @@
 
 #include <cstdio>
 
-#define WHOA_UNIMPLEMENTED()                                                                                    \
+#define WHOA_UNIMPLEMENTED(...)                                                                                 \
     fprintf(stderr, "Function not yet implemented: %s in %s (line %i)\n", __FUNCTION__, __FILE__, __LINE__);    \
-    return 0;                                                                                                   \
-    void(0)
-
-#define WHOA_UNIMPLEMENTED_VOID()                                                                               \
-    fprintf(stderr, "Function not yet implemented: %s in %s (line %i)\n", __FUNCTION__, __FILE__, __LINE__);    \
-    return;                                                                                                     \
-    void(0)
+    return __VA_ARGS__;                                                                                         \
+    (void)0
 
 #endif