fix missing import.

[MRG]Deprecated

The NULL check was there before 4b4eeaad

Skip a test with python 2.4

Manually updated scan c code version too.

This simplify the *IncSubtensor code at the same time.

IncSugtensor and the GPU code still need update.

Fix grad of Alloc when we unbroadcast an input.

This is needed for a test.

In some cases it was causing an error in the grad related to
broadcasting. In the test it case bad shape.

Gpuflatten skip test