Add Litecoin pattern

Added according to 

https://github.com/dasher/vanitygen/commit/69b66176fe9d7899922c3c6ae3f75360abdf492a#diff-2b55bd999c116ae04ed4e85e08c828abR1404

Fixes #5.
Merge pull request #6 from colindean/patch-1

Add Litecoin pattern