Make plane state values in plasma_window_management
This was seemingly used to generate C headers with wayland-scanner like
ORG_KDE_PLASMA_WINDOW_MANAGEMENT_STATE_KEEP_BELOW = 1 << 5,
However, this is suboptimal because
- It's harder to parse the XML for concrete enum values unless you attempt to generate the code in a specific way. For instance, https://docs.rs/wayland-scanner/ does it differently, hence it had to skip this XML.
- Some languages like Haskell don't even have "<<" as a bitshift operator, so it would be even more obscure for them.