Partial fix to bugzilla ticket 1140. Swept sine ramp down glitch.
Partial fix to bugzilla ticket 1140. Swept sine ramp down on abort was creating a sudden jump in amplitude. This fix positions the ramp down start time correctly in the case where the selected wave component has not yet started. To completely solve the bug, a patch to DTT to extend the ramp down period is also needed to avoid a sudden cutoff of the ramp.