Added type definitions for float, _ToRange[T], range[T], and interned

[sampersand]

This adds in the _Range[T] interface, and range[T], float, and interned aliases.

• _Range[T] is the Range equivalent of _ToInt, and is used in many places.
• range[T] is an alias for Range[T] | _Range[T], akin to string and int.
• float is an alias for Float | _ToF, which is used in quite a few places (eg Regexp#timeout=)
• interned is an alias for Symbol | string, which is frequently used, even in unexpected areas (eg Regexp#=~)

Note that I used interned instead of id, as I suspect people'll be much more likely to define id aliases, and find conflicts, than interned.

[soutaro]

👍