Add a missing `extern "C"` to slot.h.
Fixes
#ifndef __OBJC_SLOT_H_INCLUDED__
#define __OBJC_SLOT_H_INCLUDED__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
/**
* The objc_slot structure is used to permit safe IMP caching. It is returned
* by the new lookup APIs. When you call `objc_slot_lookup_version`, the final
@@ -50,4 +55,7 @@ struct objc_slot
/** Selector for this method. */
SEL selector;
} OBJC_NONPORTABLE;
+#ifdef __cplusplus
+}
+#endif
#endif // __OBJC_SLOT_H_INCLUDED__
