ncurses 6.0 - patch 20161217

+ add tput-colorcube demo script.
+ add -r and -s options to tput-initc demo, to match usage in xterm.
+ flush the standard output in _nc_flush for the case where SP is zero,
  e.g., when called via putp.  This fixes a scenario where "tput flash"
  did not work after changes in 20130112.