* Added code in 'lib/rdevent_line.cpp' and 'lib/rdsvc.cpp' to allow
embedded traffic breaks to be specified with start time and length
in the music schedule.
Changed purge_date to a QString so that it can be checked with the normal
RDCheckDateTime function. Also means the QString.isEmpty check is a straight
forward QDate.isValid and in that case we can use QDate.toString rather than
formatting via RDCheckDateTime (and incurring another QDate.isValid check).
