Unify `org-id-reverse-string' and `org-babel-reverse-string' into `org-reverse-string'

* lisp/org.el (org-reverse-string): Add `org-reverse-string' to
  reverse a string.
* lisp/org-id.el(org-id-new, org-id-decode): Replace
  `org-id-reverse-string' by `org-reverse-string'.
* lisp/ob-core.el(org-babel-trim): Replace `org-babel-reverse-string'
  by `org-reverse-string' and declare it.

TINYCHANGE

lisp/ob-core.el

@@ -93,6 +93,7 @@
 (declare-function org-escape-code-in-region "org-src" (beg end))
 (declare-function org-unescape-code-in-string "org-src" (s))
 (declare-function org-table-to-lisp "org-table" (&optional txt))
+(declare-function org-reverse-string "org" (string))
 
 (defgroup org-babel nil
   "Code block evaluation and management in `org-mode' documents."
@@ -2502,10 +2503,6 @@ If the table is trivial, then return it as a scalar."
                            (match-string 1 cell))
                       cell) t))
 
-(defun org-babel-reverse-string (string)
-  "Return the reverse of STRING."
-  (apply 'string (reverse (string-to-list string))))
-
 (defun org-babel-chomp (string &optional regexp)
   "Strip trailing spaces and carriage returns from STRING.
 Default regexp used is \"[ \f\t\n\r\v]\" but can be
@@ -2520,8 +2517,8 @@ overwritten by specifying a regexp as a second argument."
   "Strip leading and trailing spaces and carriage returns from STRING.
 Like `org-babel-chomp' only it runs on both the front and back
 of the string."
-  (org-babel-chomp (org-babel-reverse-string
-                    (org-babel-chomp (org-babel-reverse-string string) regexp))
+  (org-babel-chomp (org-reverse-string
+                    (org-babel-chomp (org-reverse-string string) regexp))
                    regexp))
 
 (defvar org-babel-org-babel-call-process-region-original nil)

lisp/org-id.el

@@ -343,7 +343,7 @@ So a typical ID could look like \"Org:4nd91V40HI\"."
       (unless (org-uuidgen-p unique)
 	(setq unique (org-id-uuid))))
      ((eq org-id-method 'org)
-      (let* ((etime (org-id-reverse-string (org-id-time-to-b36)))
+      (let* ((etime (org-reverse-string (org-id-time-to-b36)))
 	     (postfix (if org-id-include-domain
 			  (progn
 			    (require 'message)
@@ -376,9 +376,6 @@ So a typical ID could look like \"Org:4nd91V40HI\"."
 	    (substring rnd 18 20)
 	    (substring rnd 20 32))))
 
-(defun org-id-reverse-string (s)
-  (mapconcat 'char-to-string (nreverse (string-to-list s)) ""))
-
 (defun org-id-int-to-b36-one-digit (i)
   "Turn an integer between 0 and 61 into a single character 0..9, A..Z, a..z."
   (cond
@@ -432,7 +429,7 @@ and time is the usual three-integer representation of time."
     (if (= 2 (length parts))
 	(setq prefix (car parts) time (nth 1 parts))
       (setq prefix nil time (nth 0 parts)))
-    (setq time (org-id-reverse-string time))
+    (setq time (org-reverse-string time))
     (setq time (list (org-id-b36-to-int (substring time 0 4))
 		     (org-id-b36-to-int (substring time 4 8))
 		     (org-id-b36-to-int (substring time 8 12))))

lisp/org.el

@@ -21126,6 +21126,10 @@ for the search purpose."
 		(error "Unable to create a link to here"))))
     (org-occur-in-agenda-files (regexp-quote link))))
 
+(defun org-reverse-string (string)
+  "Return the reverse of STRING."
+  (apply 'string (reverse (string-to-list string))))
+
 (defun org-uniquify (list)
   "Remove duplicate elements from LIST."
   (let (res)