[windows] Move to C++. Support unicode titles. Add test.

v2/internal/ffenestri/ffenestri_windows.h

@@ -2,10 +2,13 @@
 #ifndef _FFENESTRI_WINDOWS_H
 #define _FFENESTRI_WINDOWS_H
 
+#define UNICODE 1
+
 #include "ffenestri.h"
 #include <windows.h>
 #include <wingdi.h>
 
 void center(struct Application*);
+void setTitle(struct Application* app, const char *title);
 
 #endif