fix -Wunused-but-set-variable for gcc-4.6 on x64

src/conversions-inl.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 436 matching lines @@
   const int kBufferSize = kMaxSignificantDigits + 10;
   char buffer[kBufferSize];  // NOLINT: size is known at compile time.
   int buffer_pos = 0;
 
   // Exponent will be adjusted if insignificant digits of the integer part
   // or insignificant leading zeros of the fractional part are dropped.
   int exponent = 0;
   int significant_digits = 0;
   int insignificant_digits = 0;
   bool nonzero_digit_dropped = false;
-  bool fractional_part = false;
 
   bool negative = false;
 
   if (*current == '+') {
     // Ignore leading sign.
     ++current;
     if (current == end) return JunkStringValue();
   } else if (*current == '-') {
     ++current;
     if (current == end) return JunkStringValue();
@@ skipping 82 matching lines @@
       // octal = false;
       // Integer part consists of 0 or is absent. Significant digits start after
       // leading zeros (if any).
       while (*current == '0') {
         ++current;
         if (current == end) return SignedZero(negative);
         exponent--;  // Move this 0 into the exponent.
       }
     }
 
-    // We don't emit a '.', but adjust the exponent instead.
-    fractional_part = true;
-
-    // There is a fractional part.
+    // There is a fractional part.  We don't emit a '.', but adjust the exponent
+    // instead.
     while (*current >= '0' && *current <= '9') {
       if (significant_digits < kMaxSignificantDigits) {
         ASSERT(buffer_pos < kBufferSize);
         buffer[buffer_pos++] = static_cast<char>(*current);
         significant_digits++;
         exponent--;
       } else {
         // Ignore insignificant digits in the fractional part.
         nonzero_digit_dropped = nonzero_digit_dropped || *current != '0';
       }
@@ skipping 84 matching lines @@
   ASSERT(buffer_pos < kBufferSize);
   buffer[buffer_pos] = '\0';
 
   double converted = Strtod(Vector<const char>(buffer, buffer_pos), exponent);
   return negative ? -converted : converted;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_CONVERSIONS_INL_H_