More operators are numpy expr

I tests here a the new gcc for debian (updated yesterday) is not able to compile Pythran code (internal error).
I already thought about it. I wondered if we should generate something like : `angle<T, true>(v)` instead of `angle<T>(v, true)` but then I notice that it is exactly the same as constexpr except that (for now), constexpr is for function evaluation, not for return type evaluation.
I should read more about constexpr.
Do you have any other example of this kind of function? (I mean where the return type differ)