chat must be initialized inside ME_SYSTEM_MODULESLOADED

git-svn-id: http://svn.miranda-ng.org/main/trunk@7745 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c
fix against loosing chat sessions during chat plugin's unload

git-svn-id: http://svn.miranda-ng.org/main/trunk@7746 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c