Remove MD4 unused lib

Remove MD4 unused lib
<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/yuf1011/jfs/commit/706a0603592004d5b5e3970b70755f083a215203%23commitcomment-9003751%22%5D%2C%20%22comments%22%3A%20%7B%22Commit%20706a0603592004d5b5e3970b70755f083a215203%20src/jfs/common/algorithm/MD4.java%204%205%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/yuf1011/jfs/commit/706a0603592004d5b5e3970b70755f083a215203%23commitcomment-9003751%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22test%22%2C%20%22created_at%22%3A%20%222014-12-17T06%3A58%3A36Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/8487438%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/yuf1011%22%7D%7D%5D%2C%20%22title%22%3A%20%22File%3A%20src/jfs/common/algorithm/MD4.java%3AL5%20%28706a060%29%22%7D%7D%7D'></a>
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- [ ] <a href='#crh-comment-Commit 706a0603592004d5b5e3970b70755f083a215203 src/jfs/common/algorithm/MD4.java 4 5'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/yuf1011/jfs/commit/706a0603592004d5b5e3970b70755f083a215203#commitcomment-9003751'>File: src/jfs/common/algorithm/MD4.java:L5 (706a060)</a></b>
- <a href='https://github.com/yuf1011'><img border=0 src='https://avatars.githubusercontent.com/u/8487438?v=3' height=16 width=16'></a> test


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