ncurses 6.2 - patch 20210130

ncurses 6.2 - patch 20210130

+ correct an off-by-one in comparison in waddch_literal() which caused
  scrolling when a double-cell character would not fit at the lower
  right corner of the screen (report by Benno Schulenberg).
+ split-out att610+cvis, vt220+cvis, vt220+cvis8 -TD
+ add vt220-base, for terminal emulators which generally have not
  supported att610's blinking cursor control -TD
+ use vt220+cvis in vt220, etc -TD
+ use att610+cvis, xterm+tmux and ansi+enq in kitty -TD
+ use vt220+cvis in st, terminology, termite since they ignore
  blinking-cursor detail in att610+cvis -TD