Fixed some method signatures to make them consistent with Sequence<>
Fixed some method signatures to make them consistent with Sequence<>

ceylon/ceylon.language,lucaswerkmeister/ceylon.language,jvasileff/ceylon.language,jvasileff/ceylon.language,ceylon/ceylon.language,lucaswerkmeister/ceylon.language,unratito/ceylon.language,unratito/ceylon.language