Popup: Break up placement function for reuse.
Popup arrow: Extension for making popups with arrows.
Demos: Popup arrow: New demo
Popup arrow: Use scoping instead of adding l,t,r,b classes to inner arrow elements.
Demos: Popup arrow: Create enormous anchor so clicks will work in iOS 5.
Popup arrow: Stretch the background to the width resp. height of the popup to replicate the gradient inside the arrow.
Popup arrow: Simplifying some more
Popup arrow: Theme css: Added some comments explaining the size of the arrow vs. the size of the container
Popup arrow: CSS: Save a few more bytes by replacing 0px with 0 and getting rid of arrow top/left coords, which are set programmatically anyway.

Inspired by #5594.
Popup arrow: CSS: Specify reverse transformation nicely, as a sequence of transforms, rather than as a matrix.
Popup: Declared variable twice - caught by the linter.
Popup arrow: De-linting
Popup arrow: Hack in support for IE
Popup arrow: Do not apply IE hack if box shadow is supported (pointing to IE9)
Popup arrow: Separate filter and transform, because they combine disastrously on IE9/desktop
Popup arrow: If a given side is too short to display an arrow, then do not attempt to place the arrow along that side. If no sides can have an arrow, display no arrow, but behave as a regular popup.
Popup arrow: A nicer way to restrict the IE hack to IE versions <= 8
Popup arrow: CSS: Get rid of some of the off-by-one fudging by using box-sizing: border-box
Popup arrow: Theme CSS: Set the guide offset from the border radius of ui-corner-all
Popup arrow: Simplifying decision as to whether the IE workaround is needed.