Makefile: added javadoc target

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@13473 b35dd754-fafc-0310-a699-88a17e54d16e
PingManager: Fixed imports

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@13474 b35dd754-fafc-0310-a699-88a17e54d16e
SMACK-345: Improved detection of last activity. Properly synchronized access to lastMessageSent and registerd last activity namespace with ServiceDiscoveryManager. Improved LastActivity Provider

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@13475 b35dd754-fafc-0310-a699-88a17e54d16e