Update stale link-related library names

* contrib/lisp/org-bibtex-extras.el: Update for rename of org-bibtex
to ol-bibtex.
* lisp/ox-icalendar.el: Update for rename of org-bbdb to ol-bbdb.

Reported-by: Jonas Bernoulli <jonas@bernoul.li>
<https://lists.gnu.org/archive/html/emacs-orgmode/2019-04/msg00143.html>

contrib/lisp/org-bibtex-extras.el

@@ -59,7 +59,7 @@
 ;;	 	      (obe-html-export-citations))))
 
 ;;; Code:
-(require 'org-bibtex)
+(require 'ol-bibtex)
 
 (declare-function org-trim "org" (s &optional keep-lead))
 

lisp/ox-icalendar.el

@@ -33,7 +33,7 @@
 
 (require 'cl-lib)
 (require 'ox-ascii)
-(declare-function org-bbdb-anniv-export-ical "org-bbdb" nil)
+(declare-function org-bbdb-anniv-export-ical "ol-bbdb" nil)
 
 
 
@@ -971,7 +971,7 @@ FILES is a list of files to build the calendar from."
 		files "")
 	       ;; BBDB anniversaries.
 	       (when (and org-icalendar-include-bbdb-anniversaries
-			  (require 'org-bbdb nil t))
+			  (require 'ol-bbdb nil t))
 		 (with-output-to-string (org-bbdb-anniv-export-ical)))))))
 	  (run-hook-with-args 'org-icalendar-after-save-hook
 			      org-icalendar-combined-agenda-file))