Converted push/pop to pass by ref

ee.h

@@ -18,9 +18,9 @@ struct EE_STACK_NODE {
 typedef struct EE_STACK_NODE NODE;
 typedef struct EE_STACK_NODE* STACK;
 
-STACK   push(double,STACK);
-STACK   pop(STACK);
-double  peek(STACK);
+void   push(double,STACK*);
+void   pop(STACK*);
+double  peek(STACK*);
 
 int     isNum(const char*);
 int     arrity(const char);
@@ -29,7 +29,7 @@ double  evaluate(STACK*, char);
 double* operands(STACK*, int);
 double  fact(int n);
 
-void    report();
+void    report(STACK*);