Cannot build HEAD on Gentoo

gel-ui-generic.c: In function 'set_xml_string':
gel-ui-generic.c:160:2: error: 'gtk_widget_reparent' is deprecated (declared at /usr/include/gtk-3.0/gtk/gtkwidget.h:773) [-Werror=deprecated-declarations]
  gtk_widget_reparent(w, (GtkWidget *) self);
  ^
gel-ui-dialogs.c: In function 'gel_ui_dialog_generic':
gel-ui-dialogs.c:53:3: error: 'GTK_STOCK_CLOSE' undeclared (first use in this function)
   GTK_STOCK_CLOSE, GTK_RESPONSE_CLOSE,
   ^
gel-ui-dialogs.c:53:3: note: each undeclared identifier is reported only once for each function it appears in
gel-ui-dialogs.c:78:12: error: 'GTK_STOCK_DIALOG_ERROR' undeclared (first use in this function)
    stock = GTK_STOCK_DIALOG_ERROR;
            ^
gel-ui-dialogs.c:84:2: error: implicit declaration of function 'gtk_alignment_new' [-Werror=implicit-function-declaration]
  GtkWidget *image = (GtkWidget *) gtk_alignment_new(0, 0, 0, 0);
  ^
gel-ui-dialogs.c:84:21: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  GtkWidget *image = (GtkWidget *) gtk_alignment_new(0, 0, 0, 0);
                     ^
gel-ui-dialogs.c:87:3: error: 'gtk_image_new_from_stock' is deprecated (declared at /usr/include/gtk-3.0/gtk/gtkimage.h:122): Use 'gtk_image_new_from_icon_name' instead [-Werror=deprecated-declarations]
   (GtkWidget *) gtk_image_new_from_stock(stock, GTK_ICON_SIZE_DIALOG));
   ^
gel-ui-dialogs.c:91:19: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  GtkWidget *msg = (GtkWidget *) gtk_alignment_new(0, 0, 0, 0);