swift234

Automatically inherit subobject initializers when none are explicitly defined.

If a subclass defines no subobject initializers and all of its stored
properties have initial values, "inherit" all of the subobject
initializers of its superclass by creating a new initializer with the
same signature that overrides (and chains to) the corresponding
subobject initializer of its parent. Do this instead of blindly
creating a default initializer.

Note that we aren't yet doing this for generic initializers. That will
be a separate step.

Swift SVN r14995