[Bug 38910] New: Notepad should detect if there are characters in the file which cannot be represented in the target codepage

https://bugs.winehq.org/show_bug.cgi?id=38910

Bug ID: 38910
           Summary: Notepad should detect if there are characters in the
                    file which cannot be represented in the target
                    codepage
           Product: Wine
           Version: 1.1.19
          Hardware: x86
                OS: Linux
            Status: NEW
          Keywords: download, source
          Severity: minor
          Priority: P2
         Component: programs
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

See bug 18191 for the original discussion.

Windows XP Notepad remembers the encoding of the file when it is opened, and
uses the same encoding when saving (although UTF16-BE will become UTF16-LE). If
the file is new, the default encoding is the active ANSI codepage. When saving,
if there are characters in the file which cannot be represented in the target
codepage, Notepad will put up a warning:

== Notepad ==

<filename>
  This file contains characters in Unicode format which will be lost if
 you save this file as an ANSI encoded text file. To keep the Unicode
 information, click Cancel below and then select one of the Unicode
 options from the Encoding drop down list. Continue?
   [ OK ]   [ Cancel ]

We'd want to use MultiByteToWideChar, as IsTextUnicode doesn't support utf-8.