Fix Unicode Win32 API calls in cord de_win

Fix Unicode Win32 API calls in cord de_win

* cord/tests/de_win.c (FullAppName): Remove global variable.
* cord/tests/de_win.c (szAppName): Turn into macro; use TEXT().
* cord/tests/de_win.c (de_error): Force calling ANSI version of
MessageBox; remove casts to LPSTR.
* cord/tests/de_win.c (WinMain): Use TEXT() for lpszMenuName field and
for CreateWindow agrument.
* cord/tests/de_win.c (WndProc): Use TEXT() for DialogBox argument;
force calling ANSI version of TextOut.