Add Dir#fileno since 2.2.0
Add Float#next_float and #prev_float since 2.2.0
Add Enumerable#slice_after since 2.2.0
Add argument to Enumerable#min, #min_by, #max and #max_by since 2.2.0
Add File.birthtime, #birthtime, File::Stat#birthtime and Pathname#birthtime since 2.2.0
Pathname#/ is aliased to #+ since 2.2.0