Duktape 2.X: duk_error now returns a duk_ret_t
Duktape 2.X: duk_error now returns a duk_ret_t

https://github.com/svaarala/duktape/blob/master/doc/release-notes-v2-0.rst#duk_error-duk_error_va-duk_throw-duk_fatal-have-a-return-value

This change suppress warnings about ignoring the return value.

However, it looks like we should be returning error in these cases
rather than continuing.

I'll do that in a separate commit.

kyllikki/nsgenbind,kyllikki/nsgenbind