org: Support completion of cite-related keywords

* lisp/org.el (org-get-export-keywords): Add BIBLIOGRAPHY, CITE_EXPORT,
and PRINT_BIBLIOGRAPHY to `org-options-keywords'.

It's worth noting that while based on the variable name
PRINT_BIBLIOGRAPHY may not seem to fit, it is in good company with
INCLUDE, and this variable is (exclusively) used as a list of
non-affiliated, non-block, non-export-backend-specific keywords for
pcomplete.  It may be a good idea to rename this for clarity, or split
it up in future.

lisp/org.el

@@ -8701,11 +8701,12 @@ keywords relative to each registered export back-end."
 	(push (nth 1 option-entry) keywords)))))
 
 (defconst org-options-keywords
-  '("ARCHIVE:" "AUTHOR:" "BIND:" "CATEGORY:" "COLUMNS:" "CREATOR:" "DATE:"
-    "DESCRIPTION:" "DRAWERS:" "EMAIL:" "EXCLUDE_TAGS:" "FILETAGS:" "INCLUDE:"
-    "INDEX:" "KEYWORDS:" "LANGUAGE:" "MACRO:" "OPTIONS:" "PROPERTY:"
-    "PRIORITIES:" "SELECT_TAGS:" "SEQ_TODO:" "SETUPFILE:" "STARTUP:" "TAGS:"
-    "TITLE:" "TODO:" "TYP_TODO:" "SELECT_TAGS:" "EXCLUDE_TAGS:"))
+  '("ARCHIVE:" "AUTHOR:" "BIBLIOGRAPHY:" "BIND:" "CATEGORY:" "CITE_EXPORT:"
+    "COLUMNS:" "CREATOR:" "DATE:" "DESCRIPTION:" "DRAWERS:" "EMAIL:"
+    "EXCLUDE_TAGS:" "FILETAGS:" "INCLUDE:" "INDEX:" "KEYWORDS:" "LANGUAGE:"
+    "MACRO:" "OPTIONS:" "PROPERTY:" "PRINT_BIBLIOGRAPHY" "PRIORITIES:"
+    "SELECT_TAGS:" "SEQ_TODO:" "SETUPFILE:" "STARTUP:" "TAGS:" "TITLE:" "TODO:"
+    "TYP_TODO:" "SELECT_TAGS:" "EXCLUDE_TAGS:"))
 
 (defcustom org-structure-template-alist
   '(("a" . "export ascii")