Exit with different exit code than 2 when malware hits

[WilliamDEdwards]

When malware hits > 1, maldet exits with exit code 2. I think using a dedicated exit code would be useful, so that hooks don't have to grep the output for scan completed on : [...] malware hits [...].

Maybe the EX_DATAERR sysexit would be a good choice.

I have only tested this with --scan-recent.