... not going to the cell first.

Features:
* one small fix that we needed to patch for (atomicity of CallInstruction)
* removes the ambiguous scheduling warning

size is an expression so the result would be just some other expression.

We need more vector buffers for the tail loop!

The old formula contained some 'dim's instead of '2's,
which obviously works for 2D....

Tricky... some grad components depended on the sumfac kernels of the
other directions instead of their input...