Re-worked mouse code to be devices (to allow for configuration.)

Re-worked the system pathnames (pc.c), renamed cfg_path to usr_path.
Other small things here and there.
Logitech bus mouse re-worked, should be OK now.

src/win/win_cdrom_ioctl.c

@@ -68,7 +68,7 @@ cdrom_ioctl_log(const char *format, ...)
 	va_start(ap, format);
 	vfprintf(stdlog, format, ap);
 	va_end(ap);
-	fflush(stdstdlog);
+	fflush(stdlog);
     }
 #endif
 }