Add notification counters to bottom tab

A counter now increments in the bottom bar for unfocused windows showing how
many unread messages are pending. Tabs with no pending messages show [*]
instead of their index (showing the index is useless and somewhat confusing)

src/global_commands.c

@@ -365,7 +365,7 @@ void cmd_conference(WINDOW *window, ToxWindow *self, Tox *m, int argc, char (*ar
         return;
     }
 
-    uint32_t conferencenum;
+    uint32_t conferencenum = 0;
 
     if (type == TOX_CONFERENCE_TYPE_TEXT) {
         Tox_Err_Conference_New err;