Combined FilterPointsPie and FilterPointsPie2.

Refactored FilterPointsPie and FilterPointsPie2 into a single
function that takes in an extra boolean variable (Natural).
Setting this to true makes it behave like FilterPointsPie2
did (the natural way), while false continues with the old
FilterPointsPie behavior.

These functions exported are FilterPointsPie and
FilterPointsPieEx. FilterPointsPie retains the default behavior
and parameter list, while in FilterPointsPieEx, the boolean
is exposed.

Signed-off-by: idynin <ilya@idynin.com>