Started the logic for proper positioning of the Popover on Windows.
More TODOs.
Fixed some Windows Popover redraw issues.
Removed stray TODOs.
More GTK+ Popover work. I should probably make this a proper widget.
More future plans.
Started splitting out the Popover platform-independent code.
Integrated the extracted Popover code with the Windows Popover.
Moved the Windows Popover stuff out of the way and renamed its folder to just popover/; I'll continue the GTK+ experiments here.