fixes#1398
js: 212760981493460b438f1cc117001825773fad91
https://github.com/mapbox/mapbox-gl-js/pull/1195
The sprite atlas already had two empty pixels between each each icon.
But the icon's real boundary isn't used for drawing. Drawing uses an
icon's box rounded up to the nearest multiple of four. Sometimes this
rounded boundary was directly on the edge of another icon. When the icon
was sampled with linear interpolation it's edge would get polluted with
values from the other icon.
This commit shifts all icons and glyphs by 1px so that there is padding
on all sides of the box being drawn. The quads used for drawing are
shifted in the opposite direction by 1px to compensate for this.
03d5e2da80