Test error for optional params marked 'is rw'
Test error for optional params marked 'is rw'

These were copied from t/spec/S06-signature/optional.t and modified to
test the new error message, including that the name of the parameter is
in the message. The tests in t/spec/S06-signature/optional.t will be
modified to just test that an exception is thrown (and possibly its
type), not the text of the message.

nbrown/rakudo,labster/rakudo,softmoth/rakudo,lucasbuchala/rakudo,tony-o/rakudo,awwaiid/rakudo,usev6/rakudo,MasterDuke17/rakudo,softmoth/rakudo,MasterDuke17/rakudo,tony-o/rakudo,nbrown/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,Gnouc/rakudo,sjn/rakudo,nbrown/rakudo,nbrown/rakudo,salortiz/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,tbrowder/rakudo,salortiz/rakudo,tbrowder/rakudo,sjn/rakudo,jonathanstowe/rakudo,salortiz/rakudo,Gnouc/rakudo,awwaiid/rakudo,rakudo/rakudo,lucasbuchala/rakudo,salortiz/rakudo,Gnouc/rakudo,tbrowder/rakudo,rakudo/rakudo,sjn/rakudo,raydiak/rakudo,MasterDuke17/rakudo,nbrown/rakudo,jonathanstowe/rakudo,jonathanstowe/rakudo,tony-o/rakudo,labster/rakudo,softmoth/rakudo,usev6/rakudo,usev6/rakudo,usev6/rakudo,salortiz/rakudo,raydiak/rakudo,awwaiid/rakudo,sjn/rakudo,tony-o/rakudo,rakudo/rakudo,tbrowder/rakudo,nbrown/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,Gnouc/rakudo,tony-o/rakudo,raydiak/rakudo,labster/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,rakudo/rakudo,lucasbuchala/rakudo,rakudo/rakudo,tbrowder/rakudo,softmoth/rakudo,tony-o/rakudo,jonathanstowe/rakudo,usev6/rakudo,labster/rakudo,awwaiid/rakudo,awwaiid/rakudo,salortiz/rakudo,lucasbuchala/rakudo,lucasbuchala/rakudo,raydiak/rakudo,sjn/rakudo,softmoth/rakudo,labster/rakudo