Factored Stepgen2, StepGen3 is a copy of Stepgen2

Firmware/include/StepGen2.h

@@ -50,13 +50,4 @@ public:
     uint32_t updatePos(uint32_t i);
 };
 
-class extend32to64
-{
-public:
-    int64_t previousTimeValue = 0;
-    const uint64_t ONE_PERIOD = 4294967296;  // almost UINT32_MAX;
-    const uint64_t HALF_PERIOD = 2147483648; // Half of that
-    int64_t extendTime(uint32_t in);
-};
-
 #endif