Fix doc version switch and unverbose PR GPU tests

 Fix NaNGuardMode to permit None variables

Fix GPU test_pool on Windows.

Allow for pooling of empty batch (like for conv in #3715).

[CRASH] Fix local_gpua_advanced_incsubtensor to return variable on the GPU

Cast ws, strides and pads to 64 bits integers into both Python and C code
for all these ops.

Make sure that ws, strides and pads for GpuPool, GpuMaxPoolGrad and GpuAveragePoolGrad are `npy_intp` arrays.

Fix local_gpua_advanced_incsubtensor to return variable on the GPU. op_lifer expect that. fix gh-5589

Prevent pkl_utils from stomping higher sys recursion limits

Use 64-bit indices in sparse.AddSD where necessary (fix #5525)

Scan fix

Prepare release 0.9.0rc1.

Fix reST nested lists syntax.
Fix typos.

Update .mailmap, then update count and list of contributors

[CRASH] Fix crash of GpuElemwise that have too many inputs

If there is no room for even 2 inputs, then it will fail rather than
loop endlessly.

Clarify error message related to expected kern_shape specs (1D, int64) in GpuDnnConvDesc