Fix issues in constant type declarations
Fix issues in constant type declarations

Partially addresses https://github.com/rakudo/rakudo/issues/1504

- Fixes crash with types with `::` in the name
- Fixes crash with parametarized types like `Array[Numeric]`
- Changes default type to `Mu` instead of `Any`, to match what we
    have on other variables and terms.

If $*OFTYPE is set, we try to use it as-is, stringified. However,
that's just what it looks like in code. We need to use its .ast
to actually get the type.

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