Bug 827133 - Support unavailable builds in new Sandstone Firefox languages page.

Created new unavailable CSS style for unavailable builds in languages page (display: none in 320px screens).
Added macro build_link to all.html to streamline platform column creation.
Merge pull request #570 from Elideb/bug-827133-Support-unavailable-platform

Bug 827133 - Support unavailable builds in new Sandstone Firefox languages page.