Micro-optimize Lock::Async.lock/unlock
Micro-optimize Lock::Async.lock/unlock

As these are heavily used in server applications, it seemed worthwhile to
get the 2.5% improvement.  Benchmark based on basic react / whenever listen /
whenever connection.Supply.lines -> $line block getting hammered by a single
client for 100_000 times.

softmoth/rakudo,Gnouc/rakudo,tbrowder/rakudo,softmoth/rakudo,rakudo/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo,rakudo/rakudo,softmoth/rakudo,MasterDuke17/rakudo,salortiz/rakudo,labster/rakudo,MasterDuke17/rakudo,labster/rakudo,Gnouc/rakudo,softmoth/rakudo,rakudo/rakudo,Gnouc/rakudo,nbrown/rakudo,nbrown/rakudo,MasterDuke17/rakudo,salortiz/rakudo,nbrown/rakudo,Gnouc/rakudo,labster/rakudo,rakudo/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,nbrown/rakudo,tony-o/rakudo,softmoth/rakudo,tony-o/rakudo,tony-o/rakudo,salortiz/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo,tbrowder/rakudo,rakudo/rakudo,Gnouc/rakudo,nbrown/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tony-o/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,salortiz/rakudo,salortiz/rakudo,tbrowder/rakudo,labster/rakudo,tbrowder/rakudo,nbrown/rakudo