Use wal uniformly instead of WAL

When you set the path to rocksdb directory in memory like in /dev/shm,
you need to set the wal_dir and WAL_ttl_seconds options if you want to
recover your in-memory RocksDB database after a machine reboot.

See: https://github.com/facebook/rocksdb/wiki/How-to-persist-in-memory-RocksDB-database

download zlib from github

upgrade zlib to 1.2.11

upgrade rocksdb to 5.0.1

upgrade zlib