laplacian: precalculate coordinates
laplacian: precalculate coordinates

Precalculate coordinates to avoid unneeded texture indirections.
Now laplacian works on i915.

ystreet/gst-plugins-gl,mapmapteam/gst-plugins-gl,ystreet/gst-plugins-gl,mapmapteam/gst-plugins-gl,ystreet/gst-plugins-gl,mapmapteam/gst-plugins-gl