Factor out `perf.data` parsing into a separate crate

[jonhoo]

I'm looking into building a tool to analyze and visualize perf.data files, and the parser code in https://github.com/gz/rust-perfcnt/blob/master/src/linux/parser.rs would be really handy to re-use. Would you consider factoring it out into its own crate at some point?

[gz]

Hi, First of all, sorry for not replying earlier. Last few days have been quite busy.
AFAIK you should already be able to use perfcnt as a library and include the parser from there. Is that not sufficient for your use-case? Let me know. I'm happy to make the parsing code more accessible for others.

[jonhoo]

No worries at all :)
You're right, I could do that. Given that the parsing code is entirely self-contained though, it seems like a good candidate for making its own library, which can eventually be documented and tested in isolation. This also encourages re-use, since it'll be easier for people to find a crate dedicated to parsing perf.data than to find a module hidden within a create that seems fairly unrelated.