Proposed attention API

[shellreef at gmail.com]

I committed a possible "attention" API to im.pidgin.soc.2007.msimprpl,
in revision
b888bc5c0494c9dd0398baba81e4d602ac88948f. Here is the commit message,
explaining what it is all about:

 Proposed "attention" API, a generalization of zaps (MySpaceIM), buzzes
 (Yahoo), and nudges (MSN).

 Adds a PurpleAttentionType struct to prpl.h, which is used to describe the
 the attention command (some protocols, notably MySpaceIM, support more than
 one).

 Uses two reserved fields in PurplePluginProtocolInfo, one function for sending
 an attention command, another for getting the possible attention commands
 (similar to status_types).

 Adds serv_got_attention() to server.c, similar to serv_got_im(), used to notify
 of incoming or outgoing attention notices.

A patch to libpurple is at
http://msimprpl.darkthoughts.net/attention1.diff . The full patch,
including all changes to msimprpl to use this new API, is at
http://msimprpl.darkthoughts.net/attention1-full.diff (these are both
in the same commit; unfortunately I mistakingly didn't commit each
separately). The Yahoo and MSN prpls don't currently use the new API.

What does everyone think of these changes?  I think we all can agree
that a unified attention API is a good thing, but is the way I've done
it a good way to do it? One thing I'm not sure about is the use of
reserved fields in PurplePluginProtocolInfo, and how this change would
impact libpurple's versioning.

If everyone agrees with this change, UI additions to allow using this
API (discussed in the thread starting here:
http://pidgin.im/pipermail/devel/2007-August/002468.html) would be the
next logical step.

Regards,
-Jeff