ncurses 6.0 - patch 20151010

+ add configure check for openpty to test/configure script, for ditto.
+ minor fixes to test/view.c in investigating Debian #790847.
+ update autoconf patch to 2.52.20150926, incorporates a fix for Cdk.
+ add workaround for breakage of POSIX makefiles by recent binutils
  change.
+ improve check for working poll() by using posix_openpt() as a
  fallback in case there is no valid terminal on the standard input
  (prompted by discussion on bug-ncurses mailing list, Debian #676461).