Locking litecoin wallet with JSON-RPC
Actually, Litecoin-Qt/litecoind v0.8.5.2 and probably several v0.8 releases before do support these api calls. 

The --help doesn't seem to have any entries on these commands but this is true of Bitcoin-Qt/bitcoind as well so if you want to submit a bug report or code it and submit a pull request, please do so at https://github.com/bitcoin/bitcoin.