add a 'multi-paned' widget
@matthiasc
Submitted by Matthias Clasen Link to original bug (#747581)
Description
A wishlist item from Christian Hergert:
For the editor layout in Builder, we use GtkPaned of GtkPaned (of GtkPaned). It's really annoying to manage. Additionally, it's hard to get them to always have homogenous sizing.
I'd love something that is more like a GtkBox with handles inbetween them. 1px solid line with larger dead area for gripping would be nice.
Additionally, a 2x2 paned might be interesting.