Update NSPR to 4.12 and NSS to 3.23 on iOS

nss/lib/softoken/lgglue.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/. */
 /* 
  *  The following code handles the storage of PKCS 11 modules used by the
  * NSS. This file is written to abstract away how the modules are
  * stored so we can deside that later.
  */
 #include "sftkdb.h"
 #include "sftkdbti.h"
@@ skipping 421 matching lines @@
     if (!legacy_glue_lib) {
         return CKR_OK;
     }
     if (legacy_glue_shutdown) {
 #ifdef NO_FORK_CHECK
         PRBool parentForkedAfterC_Initialize = PR_FALSE;
 #endif
         crv = (*legacy_glue_shutdown)(parentForkedAfterC_Initialize);
     }
 #ifndef NSS_STATIC
-    disableUnload = PR_GetEnv("NSS_DISABLE_UNLOAD");
+    disableUnload = PR_GetEnvSecure("NSS_DISABLE_UNLOAD");
     if (!disableUnload) {
         PR_UnloadLibrary(legacy_glue_lib);
     }
 #endif
     legacy_glue_lib = NULL;
     legacy_glue_open = NULL;
     legacy_glue_readSecmod = NULL;
     legacy_glue_releaseSecmod = NULL;
     legacy_glue_deleteSecmod = NULL;
     legacy_glue_addSecmod = NULL;
     legacy_glue_libCheckFailed    = PR_FALSE;
     legacy_glue_libCheckSucceeded = PR_FALSE;
     return crv;
 }