Multiple warnings (ignoring return value)

[der-stefan]

@hoche: Do you consider the warnings "ignoring return value" of numerous fgets and fscanf calls as relevant to be fixed? Should we add the compiler flag -Wno-unused-variable to cmake or rather catch their return values? It is desirable to compile without warnings in order to not lose sight of more important warnings like #14.

[hoche]

Those and the fgets/fscanf buffer size mismatches have been driving me crazy since I started fiddling with this code and the only reason I haven't already dealt with them is that I want to move all of that to std::string and iostreams.

As it stands now, we should be checking all those return values because that's the only way you know whether the conversion worked properly and whether you can go ahead, or need to error out, or gripe but use default values. It's not worth fixing if we're going to rewrite all that, though.