Prepare for v2.5.1

git-svn-id: https://plugins.svn.wordpress.org/cimy-swift-smtp/trunk@938912 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prepare for v2.5.1 (bis)

git-svn-id: https://plugins.svn.wordpress.org/cimy-swift-smtp/trunk@938914 b8457f37-d9ea-0310-8a92-e5e31aec5664