Remove unused "using namespace"

include/roaring/roaring64.h

@@ -388,19 +388,3 @@ bool roaring64_bitmap_iterate(const roaring64_bitmap_t *r,
 
 #endif /* ROARING64_H */
 
-#ifdef __cplusplus
-/**
- * Best practices for C++ headers is to avoid polluting global scope.
- * But for C compatibility when just `roaring.h` is included building as
- * C++, default to global access for the C public API.
- *
- * BUT when `roaring.hh` is included instead, it sets this flag. That way
- * explicit namespacing must be used to get the C functions.
- *
- * This is outside the include guard so that if you include BOTH headers,
- * the order won't matter; you still get the global definitions.
- */
-#if !defined(ROARING_API_NOT_IN_GLOBAL_NAMESPACE)
-using namespace ::roaring::api;
-#endif
-#endif