refactoring: Change struct variable name

src/inputHandling.h

@@ -10,7 +10,7 @@ op functionsType;
 char* formular;
 double inputNumbers[10];
 int arrayLength;
-void* child[10];  // all children structs which depends on this struct
+void* children[10];  // all children structs which depends on this struct
 void* parent;     // the parent struct which this struct depends on
 double result;
 }calc_op;