Use '+=' and '-=' instead of postfix ops
Use '+=' and '-=' instead of postfix ops

This is a workaround for rakudo-j, because postfix:<++>
and postfix:<--> are dying here:
https://rt.perl.org/Ticket/Display.html?id=128123#txn-1422445
tbrowder/rakudo,usev6/rakudo,rakudo/rakudo,tony-o/rakudo,awwaiid/rakudo,rakudo/rakudo,jonathanstowe/rakudo,labster/rakudo,raydiak/rakudo,salortiz/rakudo,salortiz/rakudo,samcv/rakudo,jonathanstowe/rakudo,Gnouc/rakudo,samcv/rakudo,softmoth/rakudo,rakudo/rakudo,sjn/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,rakudo/rakudo,salortiz/rakudo,awwaiid/rakudo,rakudo/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,raydiak/rakudo,sjn/rakudo,usev6/rakudo,labster/rakudo,labster/rakudo,nbrown/rakudo,samcv/rakudo,usev6/rakudo,salortiz/rakudo,jonathanstowe/rakudo,nbrown/rakudo,raydiak/rakudo,Gnouc/rakudo,jonathanstowe/rakudo,Gnouc/rakudo,salortiz/rakudo,tbrowder/rakudo,usev6/rakudo,salortiz/rakudo,awwaiid/rakudo,sjn/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,nbrown/rakudo,tony-o/rakudo,raydiak/rakudo,tbrowder/rakudo,nbrown/rakudo,tony-o/rakudo,softmoth/rakudo,samcv/rakudo,tbrowder/rakudo,tbrowder/rakudo,nbrown/rakudo,tbrowder/rakudo,tony-o/rakudo,labster/rakudo,tony-o/rakudo,sjn/rakudo,samcv/rakudo,nbrown/rakudo,Gnouc/rakudo,softmoth/rakudo,tony-o/rakudo,rakudo/rakudo,awwaiid/rakudo,sjn/rakudo,MasterDuke17/rakudo,labster/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,awwaiid/rakudo,softmoth/rakudo,labster/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,usev6/rakudo,lucasbuchala/rakudo,softmoth/rakudo,lucasbuchala/rakudo