Allow radio links after an apostrophe and mid-word

* lisp/org.el (org-make-target-link-regexp): Allow radio links after
  an apostrophe and mid-word.  Small refactoring.

* testing/lisp/test-ox.el (test-org-export/resolve-radio-link): Add
  test.

See http://permalink.gmane.org/gmane.emacs.orgmode/84108.

lisp/org.el

@@ -6179,17 +6179,13 @@ targets."
 The regular expression finds the targets also if there is a line break
 between words."
   (and targets
-       (concat
-	"\\_<\\("
-	(mapconcat
-	 (lambda (x)
-	   (setq x (regexp-quote x))
-	   (while (string-match " +" x)
-	     (setq x (replace-match "\\s-+" t t x)))
-	   x)
-	 targets
-	 "\\|")
-	"\\)\\_>")))
+       (concat "\\("
+	       (mapconcat
+		(lambda (x)
+		  (replace-regexp-in-string " +" "\\s-+" (regexp-quote x) t t))
+		targets
+		"\\|")
+	       "\\)")))
 
 (defun org-activate-tags (limit)
   (if (re-search-forward (org-re "^\\*+.*[ \t]\\(:[[:alnum:]_@#%:]+:\\)[ \r\n]") limit t)

testing/lisp/test-ox.el

@@ -2042,6 +2042,15 @@ Another text. (ref:text)
        (org-export-resolve-radio-link
 	(org-element-map tree 'link 'identity info t)
 	info))))
+  ;; Radio link next to an apostrophe.
+  (should
+   (org-test-with-temp-text "<<<radio>>> radio's"
+     (org-update-radio-target-regexp)
+     (let* ((tree (org-element-parse-buffer))
+	    (info `(:parse-tree ,tree)))
+       (org-export-resolve-radio-link
+	(org-element-map tree 'link 'identity info t)
+	info))))
   ;; Multiple radio targets.
   (should
    (equal '("radio1" "radio2")