Ops:GetItem2D&GetItemScalar to return a subtensor/scalar from a sparse matrix tested. grad() not implemented because too complicated for now

Allow data for sparse matrices to be broadcastable

A problem occurred when the data (and indices) were constant vectors of
length one, since they had a broadcastable pattern of (True,), not
(False,) as was expected. That happened in the buildbot in debug mode
with seed 24856.

Tests for tile (and some fixes besides)

TileGrad implements only one very narrow special case, and it implements
it wrongly. Raise NotImplementedError instead of using this botched
implementation.

Raise a proper error when reps is not a constant (since a tensor value
is not supported by this implementation, as it is) and also force
x.ndim == len(reps), since bad things happen if it's not the case.

Hide warnings for a past bug in the buildbot

Fix subtensor crash

Fix runtime crash with the local_subtensor_of_alloc optimization when the input have a broadcastable dimensions.

Edit NEWS.txt

Doc op

Also merge duplicate documentation of grad_sources_inputs.

PEP8 and docstring fixes.

Fix test in TrueDivTester

Since dtype mismatch is one reason the error is raised, it makes
interpreting it easier.

Fix Ger C code when output is a row or column.

Some BLAS versions did not accept (1,1) strides in that case.

Update tests, gpu_gemv is used now, not gemm/dot22