Override -hitTest: on a popover's clipping view

The clipping view should never be hit. It’s only there to clip. Without
this, Ctrl-clicking in a NSTableView or NSOutlineView in the content
view will not work (even though right-clicking does).
Merge pull request #131 from github/popover-hittest

Override -hitTest: on a popover's clipping view
Merge remote-tracking branch 'origin/master' into popover-edge-fixes
Just set ivar
style
Replace M_PI / 2 with M_PI_2
Replace NSMax uses with maxX, maxY
Clean up popover path calculations
Use next edge if screen rect doesn't contain the preferred edge
Dont use midOriginY