Added missing up and down event key to SDL demo

demo/sdl_opengl2/nuklear_sdl_gl2.h

@@ -284,6 +284,10 @@ nk_sdl_handle_event(SDL_Event *evt)
             nk_input_key(ctx, NK_KEY_TEXT_LINE_START, down && state[SDL_SCANCODE_LCTRL]);
         else if (sym == SDLK_e)
             nk_input_key(ctx, NK_KEY_TEXT_LINE_END, down && state[SDL_SCANCODE_LCTRL]);
+        else if (sym == SDLK_UP)
+            nk_input_key(ctx, NK_KEY_UP, down);
+        else if (sym == SDLK_DOWN)
+            nk_input_key(ctx, NK_KEY_DOWN, down);
         else if (sym == SDLK_LEFT) {
             if (state[SDL_SCANCODE_LCTRL])
                 nk_input_key(ctx, NK_KEY_TEXT_WORD_LEFT, down);

demo/sdl_opengl3/nuklear_sdl_gl3.h

@@ -382,6 +382,10 @@ nk_sdl_handle_event(SDL_Event *evt)
             nk_input_key(ctx, NK_KEY_TEXT_LINE_START, down && state[SDL_SCANCODE_LCTRL]);
         else if (sym == SDLK_e)
             nk_input_key(ctx, NK_KEY_TEXT_LINE_END, down && state[SDL_SCANCODE_LCTRL]);
+        else if (sym == SDLK_UP)
+            nk_input_key(ctx, NK_KEY_UP, down);
+        else if (sym == SDLK_DOWN)
+            nk_input_key(ctx, NK_KEY_DOWN, down);
         else if (sym == SDLK_LEFT) {
             if (state[SDL_SCANCODE_LCTRL])
                 nk_input_key(ctx, NK_KEY_TEXT_WORD_LEFT, down);