cursor: allow scrolling tabs/stack on title border
cursor: allow scrolling tabs/stack on title border

This allows tabbed and stacked containers to be scrolled through when
the cursor is over the border of the title bar. The borders around the
other three edges of the contents should not be affected by this change.

ascent12/sway,1ace/sway,ascent12/sway,1ace/sway,1ace/sway,ascent12/sway,SirCmpwn/sway