ncurses 6.0 - patch 20170909

+ improve wide-character implementation of myADDNSTR() in frm_driver.c,
  which was inconsistent with the normal implementation.
+ save/restore cursor position in Undo_Justification(), matching
  behavior of Buffer_To_Window() (report by Leon Winter).
+ modify test/knight to provide the "slow" solution for small screens
  using "R", noting that Warnsdorf's method is easily done with "a".
+ modify several test-programs which call use_default_colors() to
  consistently do this only if "-d" option is given.
+ additional changes to test with non-standard variants of curses:
  + modify a loop limit in firework.c to work around absense of limit
    checks in some libraries.
  + fill the last row of a window with "?" in firstlast if waddch does
    not return ERR on the lower-right corner.
+ add checks in test/configure for some functions not in 4.3BSD curses.
+ fix a regression in test/configure (cf: 20170826).