Missing IOPMLib methods and constants

[ticky]

IOPMLib is missing from this library. I’m hoping to start contributing it soon!

[dcuddeback]

@ticky That'd be great. In case you haven't seen it, there's a short blurb in the README about contributing, which basically says the source files are organized roughly the same as the C IOKit library. That makes it easier to compare side-by-side when reviewing a PR, looking for missing functionality, debugging, etc.

One thing that's come up in previous PRs is that there are slight differences in the definitions in the open source headers (the ones you'd find with Google/DuckDuckGo) and the ones that ship with XCode. When I review a PR, I compare against the header files in XCode, because those headers come from the version of the library that the compiler will link with.

Btw, I saw your comment in core-foundation-sys as well. I'll try to release that this weekend.

[ticky]

I must admit this is new territory for me, but I do plan to base it upon the headers provided in Xcode for macOS 10.13, if that’s appropriate. 😄

Thanks for the hints, though! Hopefully I can get to this soon, now that CoreFoundation-sys is building for me 😁