Update NSPR to 4.12 and NSS to 3.23 on iOS

nss/lib/util/secport.c

 /* 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/. */
 
 /*
  * secport.c - portability interfaces for security libraries
  *
  * This file abstracts out libc functionality that libsec depends on
  * 
  * NOTE - These are not public interfaces
@@ skipping 303 matching lines @@
 
     if (!pool)
         return;
     if (ARENAPOOL_MAGIC == pool->magic ) {
         len  = sizeof *pool;
         lock = pool->lock;
         PZ_Lock(lock);
     }
     if (!checkedEnv) {
         /* no need for thread protection here */
-        doFreeArenaPool = (PR_GetEnv("NSS_DISABLE_ARENA_FREE_LIST") == NULL);
+        doFreeArenaPool = (PR_GetEnvSecure("NSS_DISABLE_ARENA_FREE_LIST") == NULL);
         checkedEnv = PR_TRUE;
     }
     if (zero) {
         PL_ClearArenaPool(arena, 0);
     }
     if (doFreeArenaPool) {
         PL_FreeArenaPool(arena);
     } else {
         PL_FinishArenaPool(arena);
     }
@@ skipping 372 matching lines @@
     const unsigned char *b = (const unsigned char*) ib;
     size_t i;
     unsigned char r = 0;
 
     for (i = 0; i < n; ++i) {
         r |= *a++ ^ *b++;
     }
 
     return r;
 }