Replaced friendstatus with connectionstatus

`friendstatus` callback was returning `friendnumber` in the middle of `m_addfriend*` functions, thus without client getting the `friendnumber` from `m_addfriend*` functions yet. Here is a commit made by @Alek900 that fixed one of `m_addfriend` functions 851c52571f5024000ee17b7b41fb5ce69960104a .

The fix basically made so that the `friendstatus` callback won't ever return `FRIEND_ADDED` value. So I found it appropriate to restrict return values of the callback to only [Online, Offline] and accordingly rename the callback.