Update NSPR to 4.12 and NSS to 3.23 on iOS

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 73 matching lines @@
 **   NSPR's similar functions. The platform-native functions
 **   may not be thread safe and/or may operate on different
 **   conceptual environment space than that operated upon by
 **   NSPR's functions or other environment manipulating
 **   functions on the same platform. (!)
 ** 
 */
 NSPR_API(char*) PR_GetEnv(const char *var);
 
 /*
+** PR_GetEnvSecure() -- get a security-sensitive environment variable
+**
+** Description:
+**
+** PR_GetEnvSecure() is similar to PR_GetEnv(), but it returns NULL if
+** the program was run with elevated privilege (e.g., setuid or setgid
+** on Unix).  This can be used for cases like log file paths which
+** could otherwise be used for privilege escalation.  Note that some
+** platforms may have platform-specific privilege elevation mechanisms
+** not recognized by this function; see the implementation for details.
+*/
+NSPR_API(char*) PR_GetEnvSecure(const char *var);
+
+/*
 ** PR_SetEnv() -- set, unset or change an environment variable
 ** 
 ** Description:
 ** PR_SetEnv() is modeled on the Unix putenv() function.
 ** 
 ** Inputs: 
 **   string -- pointer to a caller supplied
 **   constant, persistent string of the form name=value. Where
 **   name is the name of the environment variable to be set or
 **   changed; value is the value assigned to the variable.
@@ skipping 35 matching lines @@
 **
 ** 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___ */