Update NSS to 3.21 RTM and NSPR to 4.11 RTM

nspr/pr/include/prenv.h

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef prenv_h___
 #define prenv_h___
 
 #include "prtypes.h"
 
@@ skipping 95 matching lines @@
 **   PRStatus.
 ** 
 ** Restrictions: 
 **   See the Restrictions documented in the description of
 **   PR_GetEnv() in this header file.
 ** 
 ** 
 */
 NSPR_API(PRStatus) PR_SetEnv(const char *string);
 
+/*
+** PR_DuplicateEnvironment() -- Obtain a copy of the environment.
+**
+** Description:
+** PR_DuplicateEnvironment() copies the environment so that it can be
+** modified without changing the current process's environment, and
+** then passed to interfaces such as POSIX execve().  In particular,
+** this avoids needing to allocate memory or take locks in the child
+** after a fork(); neither of these is allowed by POSIX after a
+** multithreaded process calls fork(), and PR_SetEnv does both.
+**
+** Inputs:
+**   none
+**
+** Returns:
+**   A pointer to a null-terminated array of null-terminated strings,
+**   like the traditional global variable "environ".  The array and
+**   the strings are allocated with PR_Malloc(), and it is the
+**   caller's responsibility to free them.
+**
+**   In case of memory allocation failure, or if the operating system
+**   doesn't support reading the entire environment through the global
+**   variable "environ" or similar, returns NULL instead.
+**
+** Restrictions:
+**   Similarly to PR_GetEnv(), this function may not interoperate as
+**   expected with the operating system's native environment accessors.
+*/
+NSPR_API(char **) PR_DuplicateEnvironment(void);
+
 PR_END_EXTERN_C
 
 #endif /* prenv_h___ */