Added missing X11 key up and down event handling

demo/x11_opengl2/nuklear_xlib_gl2.h

@@ -241,6 +241,8 @@ nk_x11_handle_event(XEvent *evt)
         else if (*code == XK_Tab)       nk_input_key(ctx, NK_KEY_TAB, down);
         else if (*code == XK_Left)      nk_input_key(ctx, NK_KEY_LEFT, down);
         else if (*code == XK_Right)     nk_input_key(ctx, NK_KEY_RIGHT, down);
+        else if (*code == XK_Up)      nk_input_key(ctx, NK_KEY_UP, down);
+        else if (*code == XK_Down)     nk_input_key(ctx, NK_KEY_DOWN, down);
         else if (*code == XK_BackSpace) nk_input_key(ctx, NK_KEY_BACKSPACE, down);
         else if (*code == XK_space && !down) nk_input_char(ctx, ' ');
         else if (*code == XK_Page_Up)   nk_input_key(ctx, NK_KEY_SCROLL_UP, down);

demo/x11_opengl3/nuklear_xlib_gl3.h

@@ -611,6 +611,8 @@ nk_x11_handle_event(XEvent *evt)
         else if (*code == XK_Tab)       nk_input_key(ctx, NK_KEY_TAB, down);
         else if (*code == XK_Left)      nk_input_key(ctx, NK_KEY_LEFT, down);
         else if (*code == XK_Right)     nk_input_key(ctx, NK_KEY_RIGHT, down);
+        else if (*code == XK_Up)        nk_input_key(ctx, NK_KEY_UP, down);
+        else if (*code == XK_Down)      nk_input_key(ctx, NK_KEY_DOWN, down);
         else if (*code == XK_BackSpace) nk_input_key(ctx, NK_KEY_BACKSPACE, down);
         else if (*code == XK_space && !down) nk_input_char(ctx, ' ');
         else if (*code == XK_Page_Up)   nk_input_key(ctx, NK_KEY_SCROLL_UP, down);