Assert initscr() returns the screen's own window, drop the NEWS entry

The test now checks the identity the review asked for. The NEWS entry goes
away because set_term(), newterm() and this code path are all new in 3.16 and
unreleased, so no user could observe the crash.

Author: fedonman

Lib/test/test_curses.py

@@ -3073,16 +3073,18 @@ def test_new_prescr(self):
         gc_collect()
 
     def test_initscr_after_newterm_keeps_screen_alive(self):
-        # initscr() called while a newterm() screen is current returns a window
-        # for that screen, and the window must keep the screen alive.  It used
-        # to be created without a screen, and using the window after the
-        # screen was collected read freed memory.
+        # initscr() called while a newterm() screen is current returns that
+        # screen's own standard window, so the window keeps the screen alive.
+        # It used to be a second wrapper created without a screen: using it
+        # after the screen was collected read freed memory, and both wrappers
+        # could delwin() the same window.
         s1 = self.make_pty()
         s2 = self.make_pty()
         screen1 = curses.newterm('xterm', s1, s1)
         screen2 = curses.newterm('xterm', s2, s2)
         curses.set_term(screen1)
         win = curses.initscr()
+        self.assertIs(win, screen1.stdscr)
         curses.set_term(screen2)
         del screen1
         gc_collect()