minor code cleanup

* removed dead code
* prevent promotion to double
* made constants constexpr
* made some methods const
* fixed a few typo's

wled00/FX_fcn.cpp

@@ -1399,17 +1399,6 @@ void Segment::refreshLightCapabilities() {
  */
 void __attribute__((hot)) Segment::fill(uint32_t c) {
   if (!isActive()) return; // not active
-  
-  #if 0 && defined(WLED_ENABLE_HUB75MATRIX) && defined(WLEDMM_FASTPATH)
-  // DIRTY HACK - this ignores the first fill(black) in each frame, knowing that HUB75 has already blanked out the display.
-  if (_firstFill) {
-    _firstFill = false;
-    if (c == BLACK) {
-      if (ledsrgb && ledsrgbSize > 0) memset(ledsrgb, 0, ledsrgbSize);
-      return;
-    }
-  }
-  #endif
 
   const uint_fast16_t cols = is2D() ? virtualWidth() : virtualLength();             // WLEDMM use fast int types
   const uint_fast16_t rows = virtualHeight(); // will be 1 for 1D