Update autotopic.c

version to v0.1.3-alpha
functional changes:
+ when someone joins the chat room, send the topic change.
+ @todo - preferencize this behavior
code changes:
+ add autotopic_send_topic_change to send the /topic commnad to the chat room.
+ modify autotopic_handle_topic_change to use autotopic_send_topic_change to change the topic.
+ add the chat-buddy-joined signal callback (chat_buddy_joined_cb)
+ add the timer callback set_topic_cb
+ chat_buddy_joined_cb sets a set_topic_cb timer whenever a new arrival joins the chatroom, using a hash table to ensure only one timer gets set for each chatroom.
+ set_topic_cb makes sure the conversation is in the hash table still, then uses autotopic_send_topic_change to set the topic.