Fleshed out a little of xlib view, cached connection links locally.
view now supports open/close again.
view_c and xlib::view_c updates.

- Split view_c into public and protected apis re: locks. It's not quite
pure yet - there is some blurryness when calling on_x, but it's significantly
more robust.
- Added support for focus and hiding the cursor.
- Implemented a large portion of xlib::view_c.