REPL6: Implement loading of alternative readline backends
REPL6: Implement loading of alternative readline backends

The Perl 6-side REPL can now try to load Readline or Linenoise,
just like Perl6::Compiler.  Completions are NYI

tbrowder/rakudo,Gnouc/rakudo,ab5tract/rakudo,tony-o/rakudo,azawawi/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,sjn/rakudo,azawawi/rakudo,usev6/rakudo,lucasbuchala/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,labster/rakudo,usev6/rakudo,zostay/rakudo,awwaiid/rakudo,Gnouc/rakudo,raydiak/rakudo,MasterDuke17/rakudo,samcv/rakudo,nbrown/rakudo,labster/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,nbrown/rakudo,azawawi/rakudo,ab5tract/rakudo,softmoth/rakudo,zostay/rakudo,samcv/rakudo,salortiz/rakudo,samcv/rakudo,salortiz/rakudo,nbrown/rakudo,softmoth/rakudo,rakudo/rakudo,awwaiid/rakudo,usev6/rakudo,tony-o/rakudo,labster/rakudo,nbrown/rakudo,tony-o/rakudo,MasterDuke17/rakudo,samcv/rakudo,awwaiid/rakudo,Gnouc/rakudo,salortiz/rakudo,rakudo/rakudo,softmoth/rakudo,b2gills/rakudo,raydiak/rakudo,lucasbuchala/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,ab5tract/rakudo,tbrowder/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,salortiz/rakudo,tony-o/rakudo,zostay/rakudo,usev6/rakudo,nbrown/rakudo,jonathanstowe/rakudo,jonathanstowe/rakudo,Gnouc/rakudo,awwaiid/rakudo,azawawi/rakudo,sjn/rakudo,tony-o/rakudo,softmoth/rakudo,b2gills/rakudo,azawawi/rakudo,salortiz/rakudo,softmoth/rakudo,rakudo/rakudo,raydiak/rakudo,raydiak/rakudo,jonathanstowe/rakudo,rakudo/rakudo,rakudo/rakudo,lucasbuchala/rakudo,sjn/rakudo,sjn/rakudo,b2gills/rakudo,lucasbuchala/rakudo,b2gills/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,nbrown/rakudo,awwaiid/rakudo,zostay/rakudo,b2gills/rakudo,samcv/rakudo,ab5tract/rakudo,labster/rakudo,sjn/rakudo,salortiz/rakudo,usev6/rakudo,labster/rakudo,tony-o/rakudo,ab5tract/rakudo