Small fixes to completion

* lisp/org-pcomplete.el (pcomplete/org-mode/file-option): Allow
  completion for ATTR_ prefixed keywords.
* lisp/org.el (org-options-keywords): Add missing colons.

lisp/org-pcomplete.el

@@ -155,7 +155,8 @@ When completing for #+STARTUP, for example, this function returns
 	      (mapc (lambda (block-name)
 		      (let ((name (car block-name)))
 			(push (format "END_%s: " name) block-names)
-			(push (format "BEGIN_%s: " name) block-names)))
+			(push (format "BEGIN_%s: " name) block-names)
+			(push (format "ATTR_%s: " name) block-names)))
 		    org-element-block-name-alist)
 	      block-names)
 	    (mapcar (lambda (keyword) (concat keyword ": "))

lisp/org.el

@@ -11563,9 +11563,9 @@ keywords relative to each registered export back-end."
 	  keywords)))
 
 (defconst org-options-keywords
-  '("ARCHIVE:" "AUTHOR:" "BIND:" "CATEGORY:" "COLUMNS:" "CREATOR:" "DATE"
+  '("ARCHIVE:" "AUTHOR:" "BIND:" "CATEGORY:" "COLUMNS:" "CREATOR:" "DATE:"
     "DESCRIPTION:" "DRAWERS:" "EMAIL:" "EXCLUDE_TAGS:" "FILETAGS:" "INCLUDE:"
-    "INDEX:" "KEYWORDS:" "LANGUAGE:" "MACRO:" "OPTIONS:" "PROPERTY"
+    "INDEX:" "KEYWORDS:" "LANGUAGE:" "MACRO:" "OPTIONS:" "PROPERTY:"
     "PRIORITIES:" "SELECT_TAGS:" "SEQ_TODO:" "SETUPFILE:" "STARTUP:" "TAGS:"
     "TITLE:" "TODO:" "TYP_TODO:" "SELECT_TAGS:" "EXCLUDE_TAGS:" "INFOJS_OPT:"))