When EOF (C-d) is received, quit interactive prompt

[Utkarsh-khambra]

std::cin.clear() does clear the eofbit, but to get stdin back to working state we also need to call clearerr, but I've made changes to just quit interactive mode when EOF is received.

(fixes #15)

[whisperity]

Oh, hah! Thank you. I'll refrain from merging this for now, because I'm doing a massive refactor (see library-refactoring, but afterwards I do expect the patch to be a trivial rebase!

[whisperity]

Just checking in to say that my life has become hectic for the ending of the semester so this'll be kept on hold for a while. I've also started working on redoing the command-line interface (together with that library refactor) to break off the dependency on getopt (as it has a weird disjoint API that bit us already, see v0.1.1) altogether. With that the interactiveness of things might be touched which will affect this functionality.

But it might be that this all will happen only during the summer... 🙁