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.

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