Small fixes

Hi Chris,

Thanks for your ArgumentParser framework, it's a great time saver to design complex command line tools.
I fixed two small issues:
- the MD5 buffers were malloced but not freed. I allocated them on the stack instead.
- the parser was logging "Unknown type: unknown" when parsing values without an equal sign (e.g., --drive n vs. --drive=n)
Feel free to merge these fixes with your code.

Best regards,
Frank