Provide a means to say "forget that request I sent"

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Sender S sends some requests to replier R.

For some reason, S realises it no longer cares about some or all of the 
replies, and would like to tell KBUS this. KBUS could then stop keeping back 
space for the (future) reply. One scenario for this is when R becomes 
unreliable, and stops responding properly to requests.

I think that if one can specify the id of the other end (i.e., R, the same id 
you used to send to them in the first place), it shouldn't be too hard for KBUS 
to ferret around in the R's "needs to send a reply to" list, and remove a 
specific query (given its message id), or all queries (given just S).

Key functions for understanding this are likely to be (in kbus_main.c) 
kbus_reply_needed, kbus_reply_now_sent and kbus_empty_replies_unsent.

Original issue reported on code.google.com by t...@kynesim.co.uk on 8 Nov 2013 at 4:11