Swift class deinit decl can be implicitly synthesized when emitting
swiftmodule, so swiftmodule always have deinit decl. So resolution of
x-refs to deinit of swift class always success.
But when x-refs points deinit of clang imported class, it always failed
because clang importer doesn't force to synthesize deinit before looking
up.
x-refs to deinit decl appears in only deinit of its subclasses, so it's
serialized only when deinit have body. And deinit has body only on SIB
because deinit is always non-inlinable. It means that this missing of
deinit creation can be problem only on SIB
This commit changes to force to synthesize class deinit
decl before looking up members.
