Fix bug in org-export-target-internal-links.

* org-exp.el (org-export-target-internal-links): Locally turn
on `org-link-search-must-match-exact-headline' to match exact
internal links.

Thanks to Jambunathan K for spotting this.

lisp/org-exp.el

@@ -1306,7 +1306,8 @@ the current file."
   (goto-char (point-min))
   (while (re-search-forward org-bracket-link-regexp nil t)
     (org-if-unprotected-at (1+ (match-beginning 0))
-     (let* ((md (match-data))
+     (let* ((org-link-search-must-match-exact-headline t)
+	    (md (match-data))
 	    (desc (match-end 2))
 	    (link (org-link-unescape (match-string 1)))
 	    (slink (org-solidify-link-text link))