Only receive clipboard offers when pasting instead of storing the data
indefinitely.
This is also more performant by default as it is not doing unnecessary
work.
This was very buggy, we were counting the events twice...
* always use pointer frame, it's available since v5
* drop axis handler
* use axis_discrete or axis_120 (v >= 8) instead
* fail on some protocol minimum version checks
* simplify output protocol version check
Fixes#120
- Double-buffer the properties.
- Fetch name, geometry and transform properties - we need these to
calculate DPI and to implement `monitor` configuration field.
Loading cursor theme and creating cursor surface are postponed to
wayland_pointer_enter because we don't know the display scale in the
early wayland_display_setup.
Partially fixes#45
