Change to LCD status indicators

The I2C LCD status indicators now indicate when the hotends or bed are
turned on at all (rather than just when they are in their heating phase)

Marlin/ultralcd_implementation_hitachi_HD44780.h

@@ -720,11 +720,11 @@ static void lcd_implementation_update_indicators()
     //set the LEDS - referred to as backlights by the LiquidTWI2 library 
     static uint8_t ledsprev = 0;
     uint8_t leds = 0;
-    if (isHeatingBed()) leds |= LED_A;
-    if (isHeatingHotend(0)) leds |= LED_B;
+    if (target_temperature_bed > 0) leds |= LED_A;
+    if (target_temperature[0] > 0) leds |= LED_B;
     if (fanSpeed) leds |= LED_C;
     #if EXTRUDERS > 1  
-      if (isHeatingHotend(1)) leds |= LED_C;
+      if (target_temperature[1] > 0) leds |= LED_C;
     #endif
     if (leds != ledsprev) {
       lcd.setBacklight(leds);