org-exp-blocks now expands blocks *after* including files

* lisp/org-exp-blocks.el (org-export-preprocess-after-include-files-hook):
  now using this hook instead of `org-export-preprocess-hook'

lisp/org-exp-blocks.el

@@ -201,7 +201,8 @@ which defaults to the value of `org-export-blocks-witheld'."
 	(interblock start (point-max))
 	(run-hooks 'org-export-blocks-postblock-hook)))))
 
-(add-hook 'org-export-preprocess-hook 'org-export-blocks-preprocess)
+(add-hook 'org-export-preprocess-after-include-files-hook
+	  'org-export-blocks-preprocess)
 
 ;;================================================================================
 ;; type specific functions