ncurses 6.0 - patch 20151017

+ modify ncurses/Makefile.in to sort keys.list in POSIX locale
  (Debian #801864, patch by Esa Peuha).
+ remove an early-return from _nc_do_color, which can interfere with
  data needed by bkgd when ncurses is configured with extended colors
  (patch by Denis Tikhomirov).
> fixes for OS/2 (patches by KO Myung-Hun)
+ use button instead of kbuf[0] in EMX-specific part of lib_mouse.c
+ support building with libtool on OS/2
+ use stdc++ on OS/2 kLIBC
+ clear cf_XOPEN_SOURCE on OS/2