Effects > Distort > Pinch and Whirl: add supersampling support
Supersampling engine: add failsafe for old Boolean quality values

If a user previously saved a Distort filter as part of a macro, the
saved quality param will be a Boolean value.  Passing TRUE to the
supersampling engine will now activate the same approach used as old PD
versions - interpolation but no supersampling - so old macros can still
work without trouble.