v1.7.3

git-svn-id: https://plugins.svn.wordpress.org/wp-performance-pack/trunk@921644 b8457f37-d9ea-0310-8a92-e5e31aec5664
wrong stable tag

git-svn-id: https://plugins.svn.wordpress.org/wp-performance-pack/trunk@921647 b8457f37-d9ea-0310-8a92-e5e31aec5664