#8 Fixes for tracker handling.

[Stephen Henson]

This patch fixes and enhances the tracker handling of
ctorrent. Specifically:

Don't send a "completed" event if file is already
complete.

Don't send "completed" event more than once.

When ctorrent closes after expiry of seed time or when
signalled with TERM or INT send a "stopped" event.

[Stephen Henson]

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There's an additional problem. Currently the tracker is only
contacted when the number of peers is less than the current
minimum number.

This can delay the accessing of the tracker for extended
periods of time and the tracker can assume the client is no
longer available (not cleanly disonnected).

[Stephen Henson]

Tracker handling fix

[Stephen Henson]

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Additional patch. Check to see if file is completed on startup
and set m_f_completed so we don't send a completed even
on an already complete file.

[Stephen Henson]

Don't send completed on alrready complete file