Fix a two bugs in Range (taking() and includesRange()) and also add a trivial optimization for skipping().
Fix a two bugs in Range (taking() and includesRange()) and also add a trivial optimization for skipping().

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