Only create the handle if we specify a device to gpu_init().

[CRASH,DOC,ENH] Mixed

mostly useless.

Fix compile on cuda < 5.0.

[CRASH] Be more resistent to NumPy bad strides for shapes of 1.

[TEST fix] Fix debugmode checking in python3

[CRASH] Conv2d none

Fix optimization error

[CRASH] Fix compilation crash in mrg on the GPU.

Force recompilation of all ops following cublas v2 interface change.

Allow to detect if we use cublas v2 or not.

Fix to the test_cross_validation.py script

[CRASH] remove assert in opt and remove print

[CRASH] fix tutorial example related to lazy evaluation.

[FIX] Fix the init/deinit of the cublas handle

[ENH] Make the gpu back-end use the new numpy c interface