fix type punned pointer warnings

main/MadgwickAHRS.cpp

@@ -21,6 +21,7 @@
 
 #include "MadgwickAHRS.h"
 #include <math.h>
+#include <string.h>
 
 //-------------------------------------------------------------------------------------------
 // Definitions
@@ -269,9 +270,12 @@ void Madgwick::updateIMU(float gx, float gy, float gz, float ax, float ay,
 float Madgwick::invSqrt(float x) {
   float halfx = 0.5f * x;
   float y     = x;
-  long  i     = *(long *)&y;
+  // long  i     = *(long *)&y;
+  long  i;
+  memcpy(&i, &y, sizeof(float));
   i           = 0x5f3759df - (i >> 1);
-  y           = *(float *)&i;
+  // y           = *(float *)&i;
+  memcpy(&y, &i, sizeof(float));
   y           = y * (1.5f - (halfx * y * y));
   y           = y * (1.5f - (halfx * y * y));
   return y;