Now that every event can unblock the loop in `event_poll` (no eof, no other input) nvim could terminate.
Consider this scenario: 
* `os_inchar` was called with `ms<0` (block until input is available) and `maxlen <3`
* The `event_poll`-loop ends because of an event.
* We cannot simulate input with the event, because `buf` is to small.
* We end up calling `read_from_input_buf` and then `read_error_exit`

Previously we would only exit the loop on "real" input.

Should one perhaps set `got_int` in this situation to prevent the termination?