Add MINTEMP/MAXTEMP error to LCD, and fix temperature bug with more then 1 extruder.

Marlin/temperature.cpp

     SERIAL_ERROR_START;
     SERIAL_ERRORLN((int)e);
     SERIAL_ERRORLNPGM(": Extruder switched off. MAXTEMP triggered !");
+    LCD_ALERTMESSAGEPGM("Err: MAXTEMP");
   }
   #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
   Stop();
     SERIAL_ERROR_START;
     SERIAL_ERRORLN((int)e);
     SERIAL_ERRORLNPGM(": Extruder switched off. MINTEMP triggered !");
+    LCD_ALERTMESSAGEPGM("Err: MINTEMP");
   }
   #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
   Stop();
   if(IsStopped() == false) {
     SERIAL_ERROR_START;
     SERIAL_ERRORLNPGM("Temperature heated bed switched off. MAXTEMP triggered !!");
+    LCD_ALERTMESSAGEPGM("Err: MAXTEMP BED");
   }
   #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
   Stop();
     {
       current_temperature_raw[0] = raw_temp_0_value;
 #if EXTRUDERS > 1
-      current_temperature_raw[1] = raw_temp_0_value;
+      current_temperature_raw[1] = raw_temp_1_value;
 #endif
 #if EXTRUDERS > 2
-      current_temperature_raw[2] = raw_temp_0_value;
+      current_temperature_raw[2] = raw_temp_2_value;
 #endif
     }