This component exports interfaces that define basic types.  These
interfaces standardize the naming of the predefined types and their
standard operations.  The interfaces will be useful as soon as
Modula-3 supports generics.

Char.def defines constants for the ASCII control characters (e.g.
Char.NUL is "\000").  It also defines the type Char.Set = SET OF
CHAR, and defines some useful Char.Set constants (e.g. Char.Digits
= {'0' .. '9'}).  Finally, it defines the type Char.Map = ARRAY
CHAR OF CHAR, and defines some useful Maps (e.g. Char.Upper[c]
converts c to upper case.)
