bugfix - use ft_selectdata to ensure that consistent selection of avg+dof is done. See http://bugzilla.fcdonders.nl/show_bug.cgi?id=2785 and thanks to Thomas


git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@10059 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0