Function permission check in SortByFunctionAndField

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7-to-database-extension/trunk@942237 b8457f37-d9ea-0310-8a92-e5e31aec5664
Version: 2.8RC8

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7-to-database-extension/trunk@942238 b8457f37-d9ea-0310-8a92-e5e31aec5664