Fix fuzzy link escaping

* lisp/org.el (org-make-link-string): Properly escape square brackets
  and percent sings in fuzzy links.

* testing/lisp/test-org-clock.el (test-org-clock/clocktable/link):
  Update tests.

Reported-by: Paulo Matos <paulo@matos-sorge.com>
<http://lists.gnu.org/r/emacs-orgmode/2017-12/msg00269.html>

lisp/org.el

@@ -9959,14 +9959,12 @@ according to FMT (default from `org-email-link-description-format')."
   (let ((uri (cond ((string-match org-link-types-re link)
 		    (concat (match-string 1 link)
 			    (org-link-escape (substring link (match-end 1)))))
-		   ;; For readability, url-encode internal links only
-		   ;; when absolutely needed (i.e, when they contain
-		   ;; square brackets).  File links however, are
-		   ;; encoded since, e.g., spaces are significant.
 		   ((or (file-name-absolute-p link)
-			(string-match-p "\\`\\.\\.?/\\|[][]" link))
+			(string-match-p "\\`\\.\\.?/" link))
 		    (org-link-escape link))
-		   (t link)))
+		   ;; For readability, do not encode space characters
+		   ;; in fuzzy links.
+		   (t (org-link-escape link (remq ?\s org-link-escape-chars)))))
 	(description
 	 (and (org-string-nw-p description)
 	      ;; Remove brackets from description, as they are fatal.

testing/lisp/test-org-clock.el

@@ -640,7 +640,7 @@ CLOCK: [2016-12-27 Wed 13:09]--[2016-12-28 Wed 15:09] => 26:00"
 |--------------+---------|
 | *Total time* | *26:00* |
 |--------------+---------|
-| [[Foo%20%5B%5Bhttp://orgmode.org%5D%5BOrg%20mode%5D%5D][Foo Org mode]] | 26:00   |"
+| [[Foo %5B%5Bhttp://orgmode.org%5D%5BOrg mode%5D%5D][Foo Org mode]] | 26:00   |"
     (org-test-with-temp-text
 	"* Foo [[http://orgmode.org][Org mode]]
 CLOCK: [2016-12-27 Wed 13:09]--[2016-12-28 Wed 15:09] => 26:00"
@@ -651,7 +651,7 @@ CLOCK: [2016-12-27 Wed 13:09]--[2016-12-28 Wed 15:09] => 26:00"
 |------------------------+---------|
 | *Total time*           | *26:00* |
 |------------------------+---------|
-| [[Foo%20%5B%5Bhttp://orgmode.org%5D%5D][Foo http://orgmode.org]] | 26:00   |"
+| [[Foo %5B%5Bhttp://orgmode.org%5D%5D][Foo http://orgmode.org]] | 26:00   |"
     (org-test-with-temp-text
 	"* Foo [[http://orgmode.org]]
 CLOCK: [2016-12-27 Wed 13:09]--[2016-12-28 Wed 15:09] => 26:00"