In the preproc window, added buttons and pull-down lists for checking
the validity of the perturbations.

Procedure: after the data screening (1st pass) is finished. Press
"reveal trial details" and go through all the F1Up trials and then
all the decel trials.

For each perturbed trial, press the "Compare in/out" button and look
at the spectrograms in the aux figure window. (Do not close this window).

Select the proper item in the pertOkay pull-down list.