WIP: Entry: Make STATE_FLAG_PRELIGHT/:hover work
[ This is WIP because:
- I don't know if anyone with influence cares enough about this to want it in GTK+ 3
- If they want it, the current implementation probably breaks stuff, so it would need
- testing to (probably) prove or disprove that
- if proving it, a direction on how to proceed instead (e.g. add a whole-widget window) ]
We were only detecting prelight on the icons but not the rest of the Entry. This commit resolves that by renaming priv->text_area to priv->event_window, extending it to cover the entire widget, replacing previous uses of text_area’s allocation with priv->text_allocation, and making ::(enter|leave)-notify detect hovering and update our StateFlags.