Make "42".Numeric about 4.3x as fast
Make "42".Numeric about 4.3x as fast

- no change for "+42"
- "42.35" about 10% slower

The speed increase is caused by (ab)using the implicit conversion
when assigning a native string to a native int if the string consists
of only numeric characters and have 18 or fewer characters.

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