swift234

SIL: Split dealloc_ref into [constructor] and [destructor] kinds

dealloc_ref [destructor] is the existing behavior. It expects the
reference count to have reached zero and the isDeallocating bit to
be set.

The new [constructor] variant first drops the initial strong
reference.

This allows DI to properly free uninitialized instances in
constructors. Previously this would fail with an assertion if the
runtime was built with debugging enabled.

Progress on <rdar://problem/21991742>.

Swift SVN r31142