Revert "Revamped the separated_list macro"
Revert "Revamped the separated_list macro"

This reverts commit 5715db59da4cdc091a40d342e1c6dd8a9ed44bc1.

This commit introduces early returns in `separated_list!`, this
breaks the expected behaviour of nom macros

meh/nom,Geal/nom,Keruspe/nom,sourrust/nom,pwoolcoc/nom,AndyShiue/nom