Activation with "softmax" leads to segfault

[simleo]

This code that used to work up to v0.8a now (v0.8.1a) leads to a segmentation fault:

layer out = Activation(Dense(l, num_classes), "softmax");

The workaround is to replace it with:

layer out = Softmax(Dense(l, num_classes));

I don't know if the intention is that the old way should still work: if so, it should be fixed. If not, it should raise some exception, rather than resulting in a segmentation fault.

Note that the old idiom still shows up in some examples.

[RParedesPalacios]

Simone, thanks, not sure what happens, Salva was working on that, let's see....

[salvacarrion]

I've fixed the examples in #232