[CSS-3] outline-style: glow

I propose to add new value of 'glow' to the list of outline-style values.

Glow is an outline where color intensity (opacity of outline-color) is a 
function of distance.
Usually glow is made by applying Gaussian 2d filter to pixels of some 
image.

Here is a sample of rendering elements with outline-style:glow;
http://www.terrainformatica.com/w3/outline-glow-sample.png

Meaning of outline-width and outline-offset when outline-style:glow :

Sum of outline-width and outline-offset gives filter radii.
outline-offset determines shape of the filter as presented here:
http://www.terrainformatica.com/w3/outline-glow-filter.png

Due to specifics of outline rendering (it is being drawn on top of 
siblings of the element)
outline is a best place to define and render such effects.

--
Andrew Fedoniouk.
http://terrainformatica.com