Slang apparently needs a call to SLsmg_refresh() to restore the screen
content and put the cursor in the right place. But call this function
only when the suspension was actually caused by an external SIGSTOP,
because otherwise the original screen (from which nano was invoked)
gets plastered with nano's interface and content -- upon exit, this
is annoying and confusing.
Do not stuff a dummy keystroke into the input stream, as it seems to
get placed *after* the first byte of the next keystroke from the user.
That would cause an "Unknown sequence" for some keystrokes.
This fixes https://savannah.gnu.org/bugs/?59077.
Bug existed since version 2.8.5, commit 84ff9ebb.
dd24f6a18d