fix: isprint => canprint

add a canprint() func that return true iif
char is ascii (< 0x80) and not a control char
(> 0x1F), as isprint() seems to be different
under Linux and Windows

dvdisaster.h

@@ -1089,6 +1089,7 @@ void CallMethodDestructors(void);
  *** misc.c 
  ***/
 
+int canprint(char);
 char* sgettext(char*);
 char* sgettext_utf8(char*);