Add c_code for MaxAndArgmax
backport to old numpy version.
Use scalar for axis or None in MaxAndArgmax.

this remove a deprecation warning in NumPy as ndarray won't be
accepted as int anymore.
Clone the NoneConst variable. Why this is needed?
Fix failing test due to optimization order.
Fix another potential reuse of NoneConst between fgraph and doc how to use it.
Merge pull request #1673 from nouiz/argmax

[MRG] Add c_code for MaxAndArgmax