swift234

Generalize the substitution of a "base type" into a reference to a
member of a oneof/struct/class/extension to support types nested
within generic classes, e.g., Vector<Int>.ElementRange. 

Most importantly, nominal types are no longer inherently canonical. A
nominal type refers to both a particular nominal type declaration as
well as its parent, which may be non-canonical and will vary. For
example, the variance in the parent makes Vector<Int>.ElementRange and
Vector<Float>.ElementRange different types. 

Introduce deduction and substitution for nominal types. Deduction is
particular interesting because we actually do allow deduction of T
when comparing X<T>.Inner and X<Int>.Inner, because (unlike C++) there
is no specialization to thwart us.



Swift SVN r2507