* gnus-sum.el (gnus-summary-backend-map): Bind B-backspace to

`gnus-summary-delete-article` in a way that also works on XEmacs.

lisp/gnus/gnus-sum.el

@@ -2220,6 +2220,7 @@ increase the score of each group you read."
   "\M-\C-e" gnus-summary-expire-articles-now
   "\177" gnus-summary-delete-article
   [delete] gnus-summary-delete-article
+  [backspace] gnus-summary-delete-article
   "m" gnus-summary-move-article
   "r" gnus-summary-respool-article
   "w" gnus-summary-edit-article