enable_sparse is indeed a Boolean

Fix composite new inputs

It happen in a particular execution order of this optimization and the
element-wise fusion optimization when upcasting some inputs to
float32 (to compute them on the gpu).
(Frederic B., reported by Sander Dieleman)

Fix for win64

New interface for scan

Gpuconv

fixed bug in min_informative_str

Fix syntax error, remove unused import.

This is temporary, as we should remove NONE_CODE ultimately.

I used to call as_tensor_variable which is not ok for sparse or
random generators

node.

sequences are not a list of dictionary anymore, but a list of tensors,
the original tensors.