Update NSPR to 4.12 and NSS to 3.23 on iOS

nss/lib/freebl/ecl/ec_naf.c

Index: nss/lib/freebl/ecl/ec_naf.c
diff --git a/nss/lib/freebl/ecl/ec_naf.c b/nss/lib/freebl/ecl/ec_naf.c
index 3db6f300f718d6a33c69b465b8116afc20103bd1..20892f09d0f87792177e94d2b7adb17f27bbc298 100644
--- a/nss/lib/freebl/ecl/ec_naf.c
+++ b/nss/lib/freebl/ecl/ec_naf.c
@@ -48,14 +48,14 @@ ec_compute_wNAF(signed char *out, int bitsize, const mp_int *in, int w)
 			/* Subtract off out[i].  Note mp_sub_d only works with
 			 * unsigned digits */
 			if (out[i] >= 0) {
-				mp_sub_d(&k, out[i], &k);
+				MP_CHECKOK(mp_sub_d(&k, out[i], &k));
 			} else {
-				mp_add_d(&k, -(out[i]), &k);
+				MP_CHECKOK(mp_add_d(&k, -(out[i]), &k));
 			}
 		} else {
 			out[i] = 0;
 		}
-		mp_div_2(&k, &k);
+		MP_CHECKOK(mp_div_2(&k, &k));
 		i++;
 	}
 	/* Zero out the remaining elements of the out array. */