curses popup single char input

curses popup single char input

With 'popup_dialog' On, a one line popup with question and likely
responses and default answer was shown, but without having the
cursor displayed at the end of emphasize that it was waiting for an
answer.  Make the popup be one character wider so that there is room
to show the cursor.  No effect when 'popup_dialog' is Off and prompts
are shown at the bottom of the message window; those already have the
cursor sitting at the end.