Non-hacky support for top-and-bottom-only (or left-and-right-only, etc.) drop shadows

Hi,

Right now box-shadow's syntax does not provide a way for specifying shadows
only for top and bottom of an element. The only way of achieving this is
using some clever hacks like the one here:
http://stackoverflow.com/a/10150898/1736621

This in turn leads to drop shadows that are brighter than what is expected.

I think apart from box-shadow, we also need box-shadow-top,
box-shadow-right, box-shadow-bottom, and box-shadow-left.

What do you think?

Please see the attached example.

 Selection_012.png<https://docs.google.com/file/d/0ByWstmU-AS9GNURTUkVMdWdWdzQ/edit>


Cheers,
Behrang Saeedzadeh
http://www.behrang.org