swift234

Switch over constructors so that they return a value instead of being a
method to initialize the members.  This doesn't matter so much
for structs (the generated IR is essentially equivalent except for
small structs), but on classes, we don't want to make "new X" generate
code that knows about metadata/destructors/etc for the class X.

Also, make sure classes always have a constructor.  (We haven't really
discussed the rules for implicitly declared constructors, so for now,
the rule is just "generate an implicit constructor if there is no
explicit constructor".  We'll want to revisit this when we actually
design object construction.)



Swift SVN r2361