Fix help for ossec-rootcheck

Added help output to match what the other binaries have. Was going to
rmeove ossec-rootcheck but found that it has been decently well
maintained through the years and has the potential to provide value.
Also, added the binary to .gitignore.
Merge pull request #281 from awiddersheim/fix_ossec_rootcheck_help

Fix help for ossec-rootcheck