rocksdb vulnerable to out-of-bounds read

Affected versions of this crate called the RocksDB C API
rocksdb_open_column_families_with_ttl() with a pointer to a single integer
TTL value, but one TTL value for each column family is expected.

This is only relevant when using
rocksdb::DBWithThreadMode::open_cf_descriptors_with_ttl() with multiple
column families.

This bug has been fixed in v0.19.0.