Backport of r59241: str.decode fails on very long strings on 64bit platforms.

PyArgs_ParseTuple t# and w# formats truncated the lengths to 32bit.
diff --git a/Misc/NEWS b/Misc/NEWS
index 30c45d1..2c9f5fd 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,11 @@
 Core and builtins
 -----------------
 
+- Issue #1521: On 64bit platforms, using PyArgs_ParseTuple with the t# of w#
+  format code incorrectly truncated the length to an int, even when
+  PY_SSIZE_T_CLEAN is set.  The str.decode method used to return incorrect
+  results with huge strings.
+
 - Issue #1445: Fix a SystemError when accessing the ``cell_contents`` 
   attribute of an empty cell object.