RubyTAPI 2.3.21.0

[Belinda Frick]

This version of RubyTAPI fixes a bug in the ringtime calculation.

Symptom
Long ring times on both live displays and reports.

Problem
Occurs when events are received for calls that have already gone
idle, and RubyTAPI considers the call as a new call. Later, when
the same call ID is re-used by TAPI, RubyTAPI has already got the
call on the list of calls, and the starting time of the call is
wrong.