Revert "Use `delete-char' instead of `delete-backward-char'"

This reverts commit 00040e708c68af0ada8ae17a74485304d3d5a817.

See this email by Achim Gratz:
http://comments.gmane.org/gmane.emacs.orgmode/52717

lisp/org-table.el

@@ -4154,7 +4154,7 @@ overwritten, and the table is not marked as requiring realignment."
 	   (looking-at "[^|\n]*  +|"))
       (let (org-table-may-need-update)
 	(goto-char (1- (match-end 0)))
-	(delete-char -1)
+	(delete-backward-char 1)
 	(goto-char (match-beginning 0))
 	(self-insert-command N))
     (setq org-table-may-need-update t)

lisp/org.el

@@ -17626,7 +17626,7 @@ overwritten, and the table is not marked as requiring realignment."
      (looking-at "[^|\n]*  |"))
     (let (org-table-may-need-update)
       (goto-char (1- (match-end 0)))
-      (delete-char -1)
+      (delete-backward-char 1)
       (goto-char (match-beginning 0))
       (self-insert-command N)))
    (t