Save to C64 PRG autoload format

still to do :
packbits packing

src/fileformats.h

@@ -118,6 +118,7 @@ void Save_C64(T_IO_Context *);
 
 void Test_PRG(T_IO_Context *, FILE *);
 void Load_PRG(T_IO_Context *);
+void Save_PRG(T_IO_Context *);
 
 // -- GPX (pixcen C64)
 void Test_GPX(T_IO_Context *, FILE *);