grate: copy vertex shader constants produced by blob
grate: copy vertex shader constants produced by blob

With this in place, for-loops with a static iterator are working now. This
is for vertex program only because I haven't seen use of those constants in
the fragment program, probably fs cannot access them and uses a separate set
of constants.

digetx/grate,grate-driver/grate,digetx/grate,grate-driver/grate