enhancement - added optional fftfilt for firws filter

git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@9989 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0
automatically synchronized identical files to revision 9989

git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@9990 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0