Support X11 systems that don't have extension libraries installed

[tomaka]

libXcursor, libXxfvm86, libXi, etc. are not necessarly available everywhere.

[robertknight]

Any idea of what real-world systems this affects? Implementing a fallback for when XInput is not available is possible but you probably only want to have to maintain that code if there is a concrete use case for it.

[tomaka]

The reason why I opened this issue is because of my raspi.
Its xinput library was not installed by default. Even when installed, it is missing some symbols and cannot be loaded. I had to remove support for xinput in glutin to make it work.

[robertknight]

That's a pretty good use case. I don't have a raspi to hand at the moment, do you know what XInput symbols are missing? I presume they are not core functionality because I've seen blogs about using XInput with touchscreen devices.

[tomaka]

The error said that XIBarrierReleasePointer was missing. Perhaps there are others, but the error only reports the first one.

Also Xcursor wasn't installed by default either.

[tomaka]

Closing for rust-windowing/winit#49