Use `backward-delete-char' instead of `delete-backward-char' to silent compiler.

* org-table.el (orgtbl-self-insert-command): Use
`backward-delete-char' instead of `delete-backward-char' as
this last command gets caught by the compiler which says to
not use it in programs.  `backward-delete-char' is just an
alias for `delete-backward-char' which is internally remapped
to `org-delete-backward-char' for optimization purpose.

* org.el (org-self-insert-command): Ditto.

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-backward-char 1)
+	(backward-delete-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-backward-char 1)
+      (backward-delete-char 1)
       (goto-char (match-beginning 0))
       (self-insert-command N)))
    (t