make the destructors virtual

modules/libimg/gifcom/nsGIFDecoder.cpp

@@ -50,7 +50,7 @@ class GIFDecoder : public nsIImgDecoder
 {
 public:
   GIFDecoder(il_container* aContainer);
-  ~GIFDecoder();
+  virtual ~GIFDecoder();
  
   NS_DECL_ISUPPORTS
 
@@ -110,7 +110,7 @@ public:
   NS_DECL_ISUPPORTS
 
   nsGIFDecFactory(const nsCID &aClass);
-  ~nsGIFDecFactory();
+  virtual ~nsGIFDecFactory();
 
   NS_IMETHOD CreateInstance(nsISupports *aOuter,
                             REFNSIID aIID,

modules/libimg/jpgcom/nsJPGCallback.h

@@ -47,7 +47,7 @@ public:
   il_container *SetContainer(il_container *ic) {mContainer=ic; return ic;};
 
   JPGCallbk(il_container *aContainer){mContainer=aContainer;};
-  ~JPGCallbk() {};	// XXX Pam needs to fix this
+  virtual ~JPGCallbk() {};	// XXX Pam needs to fix this
 
 private:
   il_container* mContainer;

modules/libimg/jpgcom/nsJPGDecoder.cpp

@@ -50,7 +50,7 @@ class JPGDecoder : public nsIImgDecoder
 {
 public:
   JPGDecoder(il_container* aContainer);
-  ~JPGDecoder();
+  virtual ~JPGDecoder();
  
   NS_DECL_ISUPPORTS
 
@@ -159,7 +159,7 @@ public:
   NS_DECL_ISUPPORTS
 
   nsJPGDecFactory(const nsCID &aClass);
-  ~nsJPGDecFactory();
+  virtual ~nsJPGDecFactory();
 
   NS_IMETHOD CreateInstance(nsISupports *aOuter,
                             REFNSIID aIID,

modules/libimg/pngcom/nsPNGCallback.h

@@ -47,7 +47,7 @@ public:
   il_container *SetContainer(il_container *ic) {mContainer=ic; return ic;};
 
   PNGCallbk(il_container *aContainer){mContainer=aContainer;};
-  ~PNGCallbk() {};	// XXX Pam needs to fix this
+  virtual ~PNGCallbk() {};	// XXX Pam needs to fix this
 
 private:
   il_container* mContainer;

modules/libimg/pngcom/nsPNGDecoder.cpp

@@ -50,7 +50,7 @@ class PNGDecoder : public nsIImgDecoder
 {
 public:
   PNGDecoder(il_container* aContainer);
-  ~PNGDecoder();
+  virtual ~PNGDecoder();
  
   NS_DECL_ISUPPORTS
 
@@ -111,7 +111,7 @@ public:
   NS_DECL_ISUPPORTS
 
   nsPNGDecFactory(const nsCID &aClass);
-  ~nsPNGDecFactory();
+  virtual ~nsPNGDecFactory();
 
   NS_IMETHOD CreateInstance(nsISupports *aOuter,
                             REFNSIID aIID,