ENH: Add `sys.prefix`/lib to library search path
ENH: Add `sys.prefix`/lib to library search path

When trying to create a `conda-forge` package of pyGLFW, I realized
that it couldn't locate the `glfw` library, which `conda` installs into
the `lib` subdirectory of `sys.prefix`. This commit adds this location
to the search path. Additionally, it slightly changes the search path
order: The priority is now
- current directory
- `pyGLFW` directory
- `sys.prefix`/lib
- "global" locations (`/usr/...` etc.)

FlorianRhiem/pyGLFW