should help identify which ares of the graph to optimize for GPU.

Updated Windows installation docs with instructions about how to get rid of the error message about assert not being declared

from previous runs, which ScanGrad would end up using

not run during import.  Running this code during import messed up the
device-switching logic (made it impossible to switch from default device).

remove useless DebugMode warning when we think we where not returning a view of the input on empty ndarray.

* number fo threads on GPU must be a multiple of NUM_VECTOR_OP_THREADS_PER_BLOCK
* this means we will have more threads on the GPU than the number of streams we
actually want.
* the fix involves making these extra threads do nothing, instead of corrupting
the stream of random samples !

TODO: review MRG_RandomStreams test suite.

implementations (on CPU). DebugMode already takes care of this.