Update IO::Path.slurp for IO::Handle changes.
Update IO::Path.slurp for IO::Handle changes.

This still tries to do some amount of fast-pathing by avoidng the cost
of the setup of a streaming decoder by opening in binary mode (or at
least, we'll do so once MoarVM's file handle support switches to be
binary only), and doing the decode in a single swoop. More may be
possible; in the meantime, this gets things working again.

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