Remove unused field Expr::marker.

src/expr.cpp

@@ -300,7 +300,6 @@ int Expr::Nodes(void) {
 Expr *Expr::DeepCopy(void) {
     Expr *n = AllocExpr();
     *n = *this;
-    n->marker = 0;
     int c = n->Children();
     if(c > 0) n->a = a->DeepCopy();
     if(c > 1) n->b = b->DeepCopy();

src/expr.h

@@ -12,7 +12,6 @@ class Expr;
 
 class Expr {
 public:
-    uint32_t marker;
 
     enum {
         // A parameter, by the hParam handle