[io grant] Make IO::Spec::Win32.is-absolute about 63x faster
[io grant] Make IO::Spec::Win32.is-absolute about 63x faster

- Use NQP ops instead of regexes
- Toss UNC path check; if we didn't match the leading slash test,
    we won't match UNC path anyway

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