LibVT+Terminal: Give TerminalWidget a hook for EOF on the pty

Instead of quitting the application immediately when the pty gives an
EOF, fire an on_command_exit hook so the TerminalWidget client can
decide for himself what to do.

Applications/Terminal/main.cpp

@@ -163,6 +163,9 @@ int main(int argc, char** argv)
 
     RefPtr<CConfigFile> config = CConfigFile::get_for_app("Terminal");
     auto terminal = TerminalWidget::construct(ptm_fd, true, config);
+    terminal->on_command_exit = [&] {
+        app.quit(0);
+    };
     terminal->on_title_change = [&](auto& title) {
         window->set_title(title);
     };