improve editbox win32

1. Do render when system DialogBox popup
2. Set password char to win32 edit control if the EditBox's input flag
is password
3. Function editBoxTextChanged will be called when the text in win32
edit control is changed
4. The temporary variable may destruct when use expression like
AnsiToUtf8(...).c_str() or Utf8ToAnsi(...).c_str() (maybe undefined
behavior)