Added virtual dtors where needed. Resolves issue #4.

Author: mikebmcl

win32/N3888_RefImpl/drawing.h

@@ -439,6 +439,8 @@ namespace std {
 				font_face& operator=(font_face&& other);
 
 				explicit font_face(native_handle_type nh);
+
+				virtual ~font_face();
 			};
 
 			class scaled_font {
@@ -581,6 +583,8 @@ namespace std {
 				pattern(pattern&& other);
 				pattern& operator=(pattern&& other);
 
+				virtual ~pattern();
+
 				status status();
 				void set_extend(extend extend);
 				extend get_extend();
@@ -616,6 +620,8 @@ namespace std {
 				gradient_pattern& operator=(const gradient_pattern&) = default;
 				gradient_pattern(gradient_pattern&& other);
 				gradient_pattern& operator=(gradient_pattern&& other);
+				virtual ~gradient_pattern();
+
 				void add_color_stop_rgb(double offset, double red, double green, double blue);
 				void add_color_stop_rgba(double offset, double red, double green, double blue, double alpha);
 				void get_color_stop_count(int& count);

win32/N3888_RefImpl/font_face.cpp

@@ -24,3 +24,6 @@ font_face& font_face::operator=(font_face&& other) {
 font_face::font_face(font_face::native_handle_type nh) {
 	_Font_face = shared_ptr<cairo_font_face_t>(nh, &cairo_font_face_destroy);
 }
+
+font_face::~font_face() {
+}

win32/N3888_RefImpl/gradient_pattern.cpp

@@ -18,6 +18,9 @@ gradient_pattern& gradient_pattern::operator=(gradient_pattern&& other) {
 	return *this;
 }
 
+gradient_pattern::~gradient_pattern() {
+}
+
 void gradient_pattern::add_color_stop_rgb(double offset, double red, double green, double blue) {
 	cairo_pattern_add_color_stop_rgb(_Pattern.get(), offset, red, green, blue);
 }

win32/N3888_RefImpl/pattern.cpp

@@ -31,6 +31,9 @@ pattern& pattern::operator=(pattern&& other) {
 	return *this;
 }
 
+pattern::~pattern() {
+}
+
 status pattern::status() {
 	return _Cairo_status_t_to_status(cairo_pattern_status(_Pattern.get()));
 }