added item base class for gold and potions

src/potion.h

@@ -5,6 +5,7 @@
 #include <memory>
 #include "fraction.h"
 #include "output.h"
+#include "item.h"
 
 enum potion_type : int;
 enum race : int;
@@ -12,7 +13,7 @@ enum race : int;
 // IMPORTANT: pop all potions of duration == 0, and when entering a
 //  new level, pop all potions of duration == -1
 
-class potion {
+class potion : public item {
 protected:
         // Use -1 to denote that the effect will last until leaving the level
         // Otherwise, use a positive number
@@ -22,10 +23,6 @@ protected:
         position pos;
         constexpr static const float DROW_POTION_MUL = 1.5f;
 public:
-        potion(const potion &p);
-        potion(potion &&p);
-        potion &operator=(const potion &p);
-        potion &operator=(potion &&p);
         potion(const potion_type type, const int duration, const position &pos);
         // apply decrements remaining_duration if it's positive, and
         //  won't do anything if it's non-negative
@@ -34,11 +31,9 @@ public:
         virtual int get_priority() const = 0;
         potion_type get_type() const;
         int get_duration() const;
-        position get_pos() const;
-        void set_pos(const position &npos);
         virtual const char *get_name() const = 0;
 
-        virtual void print(output *out);
+        void print(output *out) const override;
 };
 
 typedef std::vector<potion *> potion_list;