allow marlin internal 0°C represenation

Marlin/thermistortables.h

@@ -247,7 +247,8 @@ const short temptable_6[][2] PROGMEM = {
    {954*OVERSAMPLENR, 30},
    {970*OVERSAMPLENR, 25},
    {978*OVERSAMPLENR, 22},
-   {1008*OVERSAMPLENR, 3}
+   {1008*OVERSAMPLENR, 3},
+   {1023*OVERSAMPLENR, 0}  //to allow internal 0°C
 };
 #endif
 
@@ -307,7 +308,8 @@ const short temptable_7[][2] PROGMEM = {
    {989*OVERSAMPLENR, 20},
    {994*OVERSAMPLENR, 15},
    {1001*OVERSAMPLENR, 10},
-   {1005*OVERSAMPLENR, 5}
+   {1005*OVERSAMPLENR, 5},
+   {1023*OVERSAMPLENR, 0}  //to allow internal 0°C
 };
 #endif