Accept an anonymous integer subrange as a set base type, e.g.
'set of 0..255' or 'set of 1..10', in both the inline (var/param/field)
and 'type T = set of L..H' declaration positions. The subrange lowers to
the same bitmap machinery as 'set of Byte': the bitmap is sized to H+1
bits and member ordinals are the integer values themselves. Bounds may be
integer literals, named constants, or constant expressions; the lower
bound must be >= 0, the upper <= 255, and the range ascending.
Also fix 'set of Boolean' so a Boolean operand is accepted directly on
either side of 'in' and as the second argument of Include/Exclude, without
an intervening Ord().
Parser handles both 'set of' paths (ParseTypeName and ParseSetDef);
semantic resolution adds ResolveSubrangeSetType for on-demand and
type-decl paths. Adds dual-backend e2e tests and semantic unit tests.
Updates grammar.ebnf and language-rationale.adoc per the language-decision
rule, and removes the now-implemented item from future-improvements.adoc.
fa106ceeee