String comparison by collation as described in UTR #10
[ `Blanked | `Non_ignorable | `Shift_Trimmed | `Shifted ]
How variables are handled
[ `Primary | `Quaternary | `Secondary | `Tertiary ]
Strength of comparison. For European languages, each strength
roughly means as
`Primary : Ignore accents and case
`Secondary : Ignore case but accents are counted in.
`Tertiary : Accents and case are counted in.
For the case of `Shifted, `Shift_Trimmed, there is the fourth strength.
`Quaternary : Variables such as - (hyphen) are counted in.
module type Type =