Add os.chdir and os.setenv to d8. Move system() to os.system().

include/v8.h

 // Copyright 2007-2008 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 865 matching lines @@
   bool MakeExternal(ExternalAsciiStringResource* resource);
 
   /** Creates an undetectable string from the supplied ascii or utf-8 data.*/
   static Local<String> NewUndetectable(const char* data, int length = -1);
 
   /** Creates an undetectable string from the supplied utf-16 data.*/
   static Local<String> NewUndetectable(const uint16_t* data, int length = -1);
 
   /**
    * Converts an object to a utf8-encoded character array.  Useful if
-   * you want to print the object.
+   * you want to print the object.  If conversion to a string fails
+   * (eg. due to an exception in the toString() method of the object)
+   * then the length() method returns 0 and the * operator returns
+   * NULL.
    */
   class V8EXPORT Utf8Value {
    public:
     explicit Utf8Value(Handle<v8::Value> obj);
     ~Utf8Value();
     char* operator*() const { return str_; }
     int length() { return length_; }
    private:
     char* str_;
     int length_;
 
     // Disallow copying and assigning.
     Utf8Value(const Utf8Value&);
     void operator=(const Utf8Value&);
   };
 
   /**
    * Converts an object to an ascii string.
    * Useful if you want to print the object.
+   * If conversion to a string fails (eg. due to an exception in the toString()
+   * method of the object) then the length() method returns 0 and the * operator
+   * returns NULL.
    */
   class V8EXPORT AsciiValue {
    public:
     explicit AsciiValue(Handle<v8::Value> obj);
     ~AsciiValue();
     char* operator*() const { return str_; }
     int length() { return length_; }
    private:
     char* str_;
     int length_;
 
     // Disallow copying and assigning.
     AsciiValue(const AsciiValue&);
     void operator=(const AsciiValue&);
   };
 
   /**
    * Converts an object to a two-byte string.
+   * If conversion to a string fails (eg. due to an exception in the toString()
+   * method of the object) then the length() method returns 0 and the * operator
+   * returns NULL.
    */
   class V8EXPORT Value {
    public:
     explicit Value(Handle<v8::Value> obj);
     ~Value();
     uint16_t* operator*() const { return str_; }
     int length() { return length_; }
    private:
     uint16_t* str_;
     int length_;
@@ skipping 1586 matching lines @@
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef V8EXPORT_INLINE
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_