Update NSPR to 4.12 and NSS to 3.23 on iOS

nss/lib/freebl/mpi/mpi.c

 /*
  *  mpi.c
  *
  *  Arbitrary precision integer arithmetic library
  *
  * 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/. */
 
 #include "mpi-priv.h"
@@ skipping 1318 matching lines @@
     if(mp_cmp_z(&t) == MP_EQ)
       break;
 
     /* x = x - t       */
     if((res = mp_sub(&x, &t, &x)) != MP_OKAY)
       goto CLEANUP;
 
   }
 
   /* Copy result to output parameter */
-  mp_sub_d(&x, 1, &x);
+  MP_CHECKOK(mp_sub_d(&x, 1, &x));
   s_mp_exch(&x, b);
 
  CLEANUP:
   mp_clear(&x);
  X:
   mp_clear(&t); 
 
   return res;
 
 } /* end mp_sqrt() */
@@ skipping 1602 matching lines @@
 {
   mp_err   res;
   mp_digit dshift, bshift;
   mp_digit mask;
 
   ARGCHK(mp != NULL,  MP_BADARG);
 
   dshift = d / MP_DIGIT_BIT;
   bshift = d % MP_DIGIT_BIT;
   /* bits to be shifted out of the top word */
-  mask   = ((mp_digit)~0 << (MP_DIGIT_BIT - bshift)); 
-  mask  &= MP_DIGIT(mp, MP_USED(mp) - 1);
+  if (bshift) {
+    mask = (mp_digit)~0 << (MP_DIGIT_BIT - bshift);
+    mask &= MP_DIGIT(mp, MP_USED(mp) - 1);
+  } else {
+    mask = 0;
+  }
 
   if (MP_OKAY != (res = s_mp_pad(mp, MP_USED(mp) + dshift + (mask != 0) )))
     return res;
 
   if (dshift && MP_OKAY != (res = s_mp_lshd(mp, dshift)))
     return res;
 
   if (bshift) { 
     mp_digit *pa = MP_DIGITS(mp);
     mp_digit *alim = pa + MP_USED(mp);
@@ skipping 1846 matching lines @@
   }
   if (!pos)
     str[pos++] = 0;
   return MP_OKAY;
 } /* end mp_to_fixlen_octets() */
 /* }}} */
 
 
 /*------------------------------------------------------------------------*/
 /* HERE THERE BE DRAGONS                                                  */