proc/sys/kernel: adds support for parsing core_pattern

[danishprakash]

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Adds support for parsing /proc/sys/kernel/core_pattern.

Closes #342

[danishprakash]

@SuperQ It does seem trivial tbh. On the other hand, when I was looking for such a functionality recently, I was certain It would be something I'd find in this project. Writing a wrapper is fine with me and in fact, I was a bit skeptic about adding this myself and opened an issue(#342) beforehand to clear this up. cc: @discordianfish

[SuperQ]

Without some more useful parsing, I don't think we need this.