Platform: added no-op GlutApplication::keyReleaseEvent().

GLUT doesn't have key release events, this function is included only for
compatibility with other toolkits and doesn't get called at all.

src/Platform/GlutApplication.cpp

@@ -109,6 +109,7 @@ void GlutApplication::staticMouseMoveEvent(int x, int y) {
 }
 
 void GlutApplication::keyPressEvent(KeyEvent&) {}
+void GlutApplication::keyReleaseEvent(KeyEvent&) {}
 void GlutApplication::mousePressEvent(MouseEvent&) {}
 void GlutApplication::mouseReleaseEvent(MouseEvent&) {}
 void GlutApplication::mouseMoveEvent(MouseMoveEvent&) {}

src/Platform/GlutApplication.h

@@ -198,6 +198,14 @@ class GlutApplication {
          */
         virtual void keyPressEvent(KeyEvent& event);
 
+        /**
+         * @brief Key release event
+         *
+         * Included only for compatibility with other toolkits, doesn't get
+         * called at all.
+         */
+        virtual void keyReleaseEvent(KeyEvent& event);
+
         /*@}*/
 
         /** @{ @name Mouse handling */