Some crash fix and skip some tests when g++ isn't available.

Don't merge yet, I still have 2 tests to fix, but I'm not sure how to fix them.

The problem is that Elemwise.perform, when there is more then 32 inputs, raise an error, as numpy don't support that case. The c code support that case.

What we could do:
1) modify the optimizer, to don't create such big elemwise. But this will generate different graph if we have a compiler or not. This don't happen up to now.
2) Make a very slow and not efficient implementation of Elemwise.perform() that don't use numpy.

I think 1) is faster to implement. But I'm not sure it is a good idea. What do you think?