Add -Wnon-virtual-dtor and virtual destructors

This warning detects classes with virtual functions but a non-virtual
destructor.  Deleting instances through pointers whose type is such a
class is undefined behaviour.

I'm not certain whether any of the classes I've added the virtual
destructors to here actually needed it, but there should be negligible
performance impact, and it's a good warning to have enabled.

CMakeLists.txt

@@ -225,6 +225,7 @@ ELSE()
        -Wlogical-op \
        -Wmissing-declarations \
        -Wmissing-noreturn \
+       -Wnon-virtual-dtor \
        -Wold-style-cast \
        -Woverloaded-virtual \
        -Wpedantic \

Makefile

@@ -93,6 +93,7 @@ WARNINGS = \
   -Wlogical-op \
   -Wmissing-declarations \
   -Wmissing-noreturn \
+  -Wnon-virtual-dtor \
   -Wold-style-cast \
   -Woverloaded-virtual \
   -Wpedantic \

src/behavior_strategy.h

@@ -18,6 +18,7 @@ struct behavior_return;
 class strategy_t
 {
     public:
+        virtual ~strategy_t() = default;
         virtual behavior_return evaluate( const oracle_t *subject,
                                           std::vector<const node_t *> children ) const = 0;
 };

src/inventory_ui.h

@@ -129,6 +129,7 @@ class inventory_selector_preset
 {
     public:
         inventory_selector_preset();
+        virtual ~inventory_selector_preset() = default;
 
         /** Does this entry satisfy the basic preset conditions? */
         virtual bool is_shown( const item_location & ) const {
@@ -424,7 +425,7 @@ class inventory_selector
 {
     public:
         inventory_selector( player &u, const inventory_selector_preset &preset = default_preset );
-        ~inventory_selector();
+        virtual ~inventory_selector();
         /** These functions add items from map / vehicles. */
         void add_character_items( Character &character );
         void add_map_items( const tripoint &target );

src/item_stack.h

@@ -28,6 +28,7 @@ class item_stack
         using const_reverse_iterator = cata::colony<item>::const_reverse_iterator;
 
         item_stack( cata::colony<item> *items ) : items( items ) { }
+        virtual ~item_stack() = default;
 
         size_t size() const;
         bool empty() const;