adapt ConnctionType bwctusb to new contrast setting

server/drivers/hd44780-bwct-usb.h

@@ -14,13 +14,13 @@
 #define BWCT_LCD_SET_CONTRAST	4
 
 #define DEFAULT_SERIALNO	""
-#define DEFAULT_CONTRAST	300
 
 // initialise this particular driver
 int hd_init_bwct_usb(Driver *drvthis);
 
 void bwct_usb_HD44780_senddata(PrivateData *p, unsigned char displayID, unsigned char flags, unsigned char ch);
 void bwct_usb_HD44780_backlight(PrivateData *p, unsigned char state);
+void bwct_usb_set_contrast(Driver *drvthis, int promille);
 unsigned char bwct_usb_HD44780_scankeypad(PrivateData *p);
 void bwct_usb_HD44780_close(PrivateData *p);