Set/array literals only accepted single elements; the common Pascal
notation with ranges failed to parse ('Closing square bracket
expected'):

  if c in ['0'..'9'] then ...
  if b in [1..5, 250..255] then ...
  if f in [frBanana..frDate] then ...

ReadArray now expands constant '..' ranges into individual constant
elements while parsing. Rules match Delphi where applicable:

- both bounds must be compile-time ordinal constants of the same family
  (char/char, integer/integer, or values of the identical enum type),
- ranges can be mixed freely with single elements,
- an inverted range ('z'..'a') contributes no elements,
- a range spanning 256 or more values is rejected (a set cannot hold
  more), reported as a type mismatch.

Dynamic bounds stay unsupported (they would require runtime set
construction); the bounds must be constants, mirroring the previous
all-constant behaviour of set literals.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>