Add new printf patterns to make-pot

This script is used to extract our strings for translators
on damn lines, and passing these flags to xgettext makes
it put a hint into the pot file about strings that are
used as printf format strings.

make-pot

@@ -60,6 +60,7 @@ $XGETTEXT --default-domain="$GETTEXT_PACKAGE" \
           --flag=gtk_message_dialog_format_secondary_text:2:c-format \
           --flag=gtk_message_dialog_new:5:c-format \
           --flag=gtk_message_dialog_new_with_markup:5:c-format \
+          --flag=gtk_alert_dialog_new:1:c-format \
           --files-from="$srcdir/POTFILES.in" \
         && test ! -f "$GETTEXT_PACKAGE.po" \
            || ( rm -f "$srcdir/$GETTEXT_PACKAGE.pot" \