Comment 55 for bug 1662544

This patch fixes DND. Should be tested at least from Nautilus and from Firefox (different code paths are executed in those cases).

The patch looks big, but it isn't. Most of this is indentation fix, I moved a part of the code one level deeper, to the only branch where it can be executed. It was an obvious followup of the tiny reorganization at the MOZ vs. non-MOZ branch which I had to do anyway.

feed_child() takes a bytes object instead of str, I don't know why, so I had to encode there to make other use cases, such as "Insert terminal number" work too. Also I had to switch to feed_child_binary() for other reasons, namely https://gitlab.gnome.org/GNOME/vte/issues/201, which has the lucky consequence that the bug about the wrong number of parameters being passed to feed_child() is also gone – well, gone partially, there's another place in the source where that needs to be fixed, probably using the same one-liner trick as here.