Add a function to the native context that loads the functions using `CStr` instead of `str`

[notgull]

I'm not particularly attached to the name

[grovesNL]

Thanks! Looks like CI is failing on this.

This change seems reasonable, but just curious about the use case for loading with CStr instead. Are you using something other than the common loaders (e.g. glutin, sdl2)?

[notgull]

Whoops! This should hopefully fix it.

I was writing a wrapper around WGL and wanted to use this crate. I am definitely not writing my own OpenGL implementation.

[bors[bot]]

Build succeeded:

• build (beta)
• build (macos)
• build (nightly)
• build (pinned)
• build (stable)
• build (windows)