Strict conformance to numpy's complex handling

std::complex and numpy complex behave in slightly different ways...
See pythran/pythonic/patch/README.rst for the motivation and choices.
> Skip TypeError? It looks like we will have the same issue that what we had with
> numpy two month ago....

I don't think so: there are still a lot of tests after this try...except
block. The type error is raised here if ``ref`` or ``res`` are, e.g. strings. In
that case isinf is notdefined, but the later checks are still applied.