unify x11/x11-dl crates with dlib

[Be-ing]

Since #7, the x11-dl crate uses dlopen instead of direct linking. This split of crates is odd and confusing. I think dlib would be a better solution. It allows the user of the library to decide at build time via a Cargo option whether to link or dlopen.

[AltF02]

Yeah I was looking into maybe using bindgen aswell

There's just an small issue unifying, alot of packages depend on x11-dl, which means that I would probably have to deploy 2 packages per version. I could maybe a warning in the build.rs though

[Be-ing]

Yeah, I suggest to put

compile_error!("This crate has been unified with the x11 crate. Switch to the x11 crate and enable its `dlopen` feature.");

in x11-dl's build.rs when releasing the merged crate.