Mark Rake::AltSystem for deprecation
Mark Rake::AltSystem for deprecation

Also, hide it from documentation because nobody should be looking at it
or using it.

taiganakagawa/rake,ruby/rake,utilum/rake,pjump/rake,88rabbit/rake,Vanzct/rake,bentley/rake,codedogfish/rake,ipmobiletech/rake,ruby/rake,esasse/rake,envato/rake,tmornini/rake,envato/rake,jaustinhughey/rake,askl56/rake,zzak/rake