fix: add extern and ROCKSDB_LIBRARY_API to two c apis (#11217)

Summary:
add extern and `ROCKSDB_LIBRARY_API ` to `rocksdb_property_int` and `rocksdb_property_int_cf`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11217

Reviewed By: cbi42

Differential Revision: D43522968

Pulled By: ajkr

fbshipit-source-id: 4cd4e136f3890fc17e0a1f9e7ac4e517e4d79afa

include/rocksdb/c.h

@@ -599,12 +599,13 @@ extern ROCKSDB_LIBRARY_API void rocksdb_release_snapshot(
 extern ROCKSDB_LIBRARY_API char* rocksdb_property_value(rocksdb_t* db,
                                                         const char* propname);
 /* returns 0 on success, -1 otherwise */
-int rocksdb_property_int(rocksdb_t* db, const char* propname,
+extern ROCKSDB_LIBRARY_API int rocksdb_property_int(rocksdb_t* db,
+                                                    const char* propname,
                                                     uint64_t* out_val);
 
 /* returns 0 on success, -1 otherwise */
-int rocksdb_property_int_cf(rocksdb_t* db,
-                            rocksdb_column_family_handle_t* column_family,
+extern ROCKSDB_LIBRARY_API int rocksdb_property_int_cf(
+    rocksdb_t* db, rocksdb_column_family_handle_t* column_family,
     const char* propname, uint64_t* out_val);
 
 extern ROCKSDB_LIBRARY_API char* rocksdb_property_value_cf(