PCBC-240: Fixup API descr of return value for touch

Change-Id: I6e2140d2212af5b967bb424ba7346ed792e4d3dd
Reviewed-on: http://review.couchbase.org/28568
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>

Author: trondn

example/couchbase-api.php

@@ -521,7 +521,8 @@ function unlock($id, $cas) {
      *
      * @param string $id identifies the document
      * @param integer $expiry the new time to live (0 == infinite)
-     * @return boolean true upon success
+     * @return string containing the cas value (note some servers will
+     *                will always return "0" for the cas value)
      * @throws CouchbaseException if an error occurs
      */
     function touch($id, $expiry) {