Cleanup: make remaining blenlib headers work in C++

Differential Revision: https://developer.blender.org/D6988

Reviewers: brecht

source/blender/blenlib/BLI_array_store_utils.h

@@ -21,6 +21,10 @@
  * \ingroup bli
  */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct BArrayStore;
 
 struct BArrayStore_AtSize {
@@ -40,4 +44,8 @@ void BLI_array_store_at_size_calc_memory_usage(struct BArrayStore_AtSize *bs_str
                                                size_t *r_size_expanded,
                                                size_t *r_size_compacted);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* __BLI_ARRAY_STORE_UTILS_H__ */