Fix compilation with GCC 5.2

src/bignum.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bignum.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 50 matching lines @@
     bigits_[i] = 0;
   }
   used_digits_ = other.used_digits_;
 }
 
 
 static uint64_t ReadUInt64(Vector<const char> buffer,
                            int from,
                            int digits_to_read) {
   uint64_t result = 0;
-  for (int i = from; i < from + digits_to_read; ++i) {
+  int to = from + digits_to_read;
+
+  for (int i = from; i < to; ++i) {
     int digit = buffer[i] - '0';
     DCHECK(0 <= digit && digit <= 9);
     result = result * 10 + digit;
   }
   return result;
 }
 
 
 void Bignum::AssignDecimalString(Vector<const char> value) {
   // 2^64 = 18446744073709551616 > 10^19
@@ skipping 661 matching lines @@
     bigits_[i] = difference & kBigitMask;
     borrow = difference >> (kChunkSize - 1);
   }
   Clamp();
   DCHECK(Bignum::Equal(a, *this));
 }
 
 
 }  // namespace internal
 }  // namespace v8