Blender Git Loki

Fix T41639, hierarchical pie menu - popup interaction is buggy.

Basically, this commit changes pie menu click interaction so that
confirmation is done on left click release instead of press. This allows
dragging on the pie menu to select different items, but most
importantly, there should be no left over click events passed on to
subsequent menus/pies. This means that pie menus should now be able to
spawn popups safely. Also, left clicking to spawn a second pie menu now
sets that menu to click style by default allowing for better interaction
between hierarhies of pie menus.