Remove grab-bag includes of v8.h from several files.

src/bignum-dtoa.h

 // Copyright 2010 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.
 
 #ifndef V8_BIGNUM_DTOA_H_
 #define V8_BIGNUM_DTOA_H_
 
+#include "src/vector.h"
+
 namespace v8 {
 namespace internal {
 
 enum BignumDtoaMode {
   // Return the shortest correct representation.
   // For example the output of 0.299999999999999988897 is (the less accurate but
   // correct) 0.3.
   BIGNUM_DTOA_SHORTEST,
   // Return a fixed number of digits after the decimal point.
   // For instance fixed(0.1, 4) becomes 0.1000
@@ skipping 31 matching lines @@
 //   which case the caller has to fill the missing digits with '0's.
 //   Halfway cases are again rounded up.
 // 'BignumDtoa' expects the given buffer to be big enough to hold all digits
 // and a terminating null-character.
 void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
                 Vector<char> buffer, int* length, int* point);
 
 } }  // namespace v8::internal
 
 #endif  // V8_BIGNUM_DTOA_H_