StdModel/Pipeline: remove unused feature attributes as GL implementation can and do remove them
StdModel/Pipeline: remove unused feature attributes as GL implementation can and do remove them

Of course the behaviour differs, in this case the vertex shader was
using the attribute but not the fragment shader, which only certain GL
implementations used as an optimisation point (certain Linux/Android
ones)

zenmumbler/stardazed-tx,zenmumbler/libzm,stardazed/stardazed-tx,stardazed/stardazed,zenmumbler/libzm,zenmumbler/libzm,stardazed/stardazed-tx,zenmumbler/stardazed-tx,stardazed/stardazed-tx,zenmumbler/stardazed-tx,stardazed/stardazed,zenmumbler/stardazed-tx,zenmumbler/libzm