Make ConvOp propagate any available shape information to instantiated gradient ops
make local_gpu_alloc_memset_0() keep the original broadcast pattern
Fix ConvOp shape inference and propagation for imshp=None
pep8
add check before patternbroadcast in local_gpualloc_memset_0
Merge pull request #2103 from f0k/convop-grad-shapes

Propagate shape information to ConvOp gradients