Improve String::WriteAscii and add PRESERVE_ASCII_NULL option.

include/v8.h

 // Copyright 2012 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 1046 matching lines @@
    * \param nchars_ref The number of characters written, can be NULL.
    * \param options Various options that might affect performance of this or
    *    subsequent operations.
    * \return The number of characters copied to the buffer excluding the null
    *    terminator.  For WriteUtf8: The number of bytes copied to the buffer
    *    including the null terminator (if written).
    */
   enum WriteOptions {
     NO_OPTIONS = 0,
     HINT_MANY_WRITES_EXPECTED = 1,
-    NO_NULL_TERMINATION = 2
+    NO_NULL_TERMINATION = 2,
+    PRESERVE_ASCII_NULL = 4
   };
 
   // 16-bit character codes.
   V8EXPORT int Write(uint16_t* buffer,
                      int start = 0,
                      int length = -1,
                      int options = NO_OPTIONS) const;
   // ASCII characters.
   V8EXPORT int WriteAscii(char* buffer,
                           int start = 0,
@@ skipping 3456 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_