Cleaned up non-standard characters

Marlin/Marlin_main.cpp

 // M500 - stores paramters in EEPROM
 // M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).  
 // M502 - reverts to the default "factory settings".  You still need to store them in EEPROM afterwards if you want to.
-// M503 - print the current settings (from memory not from eeprom)
+// M503 - print the current settings (from memory not from eeprom)
 // M540 - Use S[0|1] to enable or disable the stop SD card print on endstop hit (requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
 // M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
 // M907 - Set digital trimpot motor current using axis codes.

Marlin/thermistortables.h

    {970*OVERSAMPLENR, 25},
    {978*OVERSAMPLENR, 22},
    {1008*OVERSAMPLENR, 3},
-   {1023*OVERSAMPLENR, 0}  //to allow internal 0°C
+   {1023*OVERSAMPLENR, 0}  //to allow internal 0 degrees C
 };
 #endif
 
    {994*OVERSAMPLENR, 15},
    {1001*OVERSAMPLENR, 10},
    {1005*OVERSAMPLENR, 5},
-   {1023*OVERSAMPLENR, 0}  //to allow internal 0°C
+   {1023*OVERSAMPLENR, 0}  //to allow internal 0 degrees C
 };
 #endif
 #if (THERMISTORHEATER_0 == 8) || (THERMISTORHEATER_1 == 8) || (THERMISTORHEATER_2 == 8) || (THERMISTORBED == 8)