Minor stuff (PEP8 and typos mostly)

Mixed

Cleanup of sparse/basic.py

Fix defaults

fixed debugging and warning messages (grammar and semantics) for cudandarray

previously, it stored the initial value of shared variables in defaults
this wasted a lot of memory
now it does not

Minor stuff

ndarray

Similar lists were added recently in elemwise.py: it is better to re-use
existing ones.

Fixed infinite canonizer loop with NaN constants