solved some compiler warnings that are now visible in arduino 1.0.

Found a couple of unused variables, that I commented.
Tried to solve the program memory warning message, and failed.

Marlin/Marlin.pde

@@ -167,7 +167,8 @@ static char *strchr_pointer; // just a pointer to find chars in the cmd string l
 
 const int sensitive_pins[] = SENSITIVE_PINS; // Sensitive pin list for M42
 
-static float tt = 0, bt = 0;
+//static float tt = 0;
+//static float bt = 0;
 
 //Inactivity shutdown variables
 static unsigned long previous_millis_cmd = 0;